Please can someone explain the ending?

Well I think basically Carty had got the aggression out of his system and started using his brain again, but his jaunt into thuggery couldn't go unpunished so he was left with a wound. He got out too late. He decided he'd had enough before Baby cut him though I think. I assume Elvis jumped.

I've only seen the film once, but I think the final line was "how long had I waited for this day?", and I think that was signalled a moment of clarity for Carty, in all sorts of ways. I think ultimately that wound gave him the push he needed to walk away, and by doing that he found some inner peace, as he had stopped trying to belong to something he couldn't and accepted who he was. That's my interpretation anyway.