I'm going to be the guy nobody agrees with here so get ready to do some relaxation techniques:
i only hit him once so it was even anyways, but his parents are being richards and like "hurr if this needs surgery YOU PAY"
jesus christ what stuffty parents
That's not self defense, that was revenge
If he's really as wimpy as you described him then you could have easily gotten out of the way of any other rocks he threw, or maybe just knocked him down or something.
In what world is- a skinny, annoying, jerk throwing a rock = literally breaking someone's face
That is extremely uncalled for. Obviously the guy has terrible parents, so he probably hasn't had the best childhood. He probably has no friends, and he's just some kid threatening to take your girlfriend, which is never going to happen anyways. The only thing he really did worth getting upset over is throwing a rock, and that is still not half as bad as breaking someone's skull. I understand that some people have legitimate impulse control disorders, and you could be one of them, but it seems like it's just code for having zero self control a lot of the time