This is typical, you're not alone. Millions of people get picked on, they get beat up, they get treated badly... I had that happen a lot to me when I was young, it's sad but that's the way many people are.
It's unfortunate that you had an injury as a result. I don't know much about how the law works here in the UK, but in the US you can sue that kid if you can prove that the damages were caused by him. Of course he doesn't have money, so you would actually be suing his parents... That's side-tracking a little, but something to think about.
However, as far as the psychological aspects are concerned, here is the best advice I can give you, so listen carefully.
You only live once, as far as anyone knows... Who you are is who you will be for the rest of your life. Whatever happens today, will begin drowning in the past tomorrow. No matter how long the effects of any circumstance or instance are they will eventually be forgotten. One day, you will die, just like me, just like everyone, and when you die, some people will remember you, but eventually you'll be forgotten by everyone. Does it really matter what people think of you? Just live your life the way that you want to live it, and try your best to enjoy it, because it's all you've got, and it's up to you to make the most of it. Life is hard, you're going to get a hell of a lot more angry when you get older and have to deal with idiots all day every day. You'll realize that the majority of people around you are morons, because it's statistics that the majority of people drop out of school, or get involved in the wrong things, and treat people badly, and just don't care about other people's feelings. This is a sad fact of life that you, I, and everyone will eventually come to understand. It's best for you to understand it now while you're young.
Time goes by very quickly, before you know it, you'll be 20... Then you'll be 40... and so on. Make the most of NOW, TODAY, HERE. Don't wait for tomorrow, because honestly it may never come. You never know what is going to happen. If there's someone outside your door, then talk to them if you want to, or don't talk to them if you can't, it doesn't matter... do what you can, and don't ever have any regrets or dwell on the past... If you don't care about the person outside of your door, the to be honest, screw them,
lol. Try your best to be happy, don't hurt yourself, and don't hurt others... I find it helps to believe in something called "Karma", if you have the mind-frame that "what comes around, goes around" then it will make you feel better when someone wrongs you... Let me give an example that suits you...
That moron bully who hit you... I bet he was picked on as a child, maybe his parents beat him or worse... That's not something you should wish to happen to someone, of course, but if it did, wouldn't it make you feel sorry for him? If it doesn't make you feel sorry for him, then you lack compassion for others, which is okay, if that's who you want to be, but re-evaluate yourself, ask yourself: "Is that who I want to be?" Do you want to lack compassion? If you don't care, then fine, but be sincere about it, because maybe you will feel better about yourself if you spend more time thinking about others. Back to the example at hand... So maybe the Bully wasn't mistreated, maybe you have no reason to feel sorry for him at all... He hit you, and you don't want to forgive him for it, you want revenge, but you don't have the guts to punch him back, or maybe you want to be the bigger man and not punch him back, because afterall, what is that going to get you? In trouble. Fighting is really stupid, UNLESS it's for sport (UFC is awesome), OR if it's to defend yourself or others... But fighting for "honor" and "pride" is pointless... Maybe a year from now that bully will get in a position that makes him very uncomfortable... Maybe he'll lose his job, fail at something he expected to succeed in, or maybe someone will put him in his place and beat him up, knock his teeth out or something... Because if he runs around acting tough and punching people, then he is eventually going to get what he deserves.
Listen buddy, try to be the best person you can be... Take deep breaths when you feel angry... Try to release your anger... try to become less angry... Figure out what's making you angry and try to get rid of it. Do the best you can in life, and you will have nothing to worry about... you shouldn't feel bad about anything. Forgive yourself for your mistakes, and forgive other people for their mistakes. As long as you learn from your mistakes, you're moving in the right direction, and you should be proud of yourself. No matter what happens, make the most of it. If this still isn't good enough, then try to think about other people who are in worse situations than you are...
You got punched in the neck, you have minor annoying problems, but nothing too serious as far as you know...
But some poor guy just got beat up and had to watch his girlfriend get beat up, then the people stole everything from them.... DAMN that's bull
!!! That makes me angry, and it didn't even happen to me! But guess what? That's the evil world we live in. Just be glad you aren't THAT guy...
Take care and I hope you can find a way to live your life and not let anything bother you so much... Just be grateful for who you are and what you have... things could be much worse...