So, I guess I should start by giving some background information first;

On my neighborhood there is this one little kid, 13 or 14. He is the most rude person I have seen in my life: insults old people, yells at ALL times, curses for everything, treats his mother like absolute crap and is just generally as obnoxious as anyone can get. I think he even got into trouble with the police once. I've spoken to some  neighbors and they are actually amazed someone can be as spoiled and rude as that kid is.

The thing is, I was biking the other day next to a skate park and the kid was there. I prefer to ignore him so that's what I did, as usual. Now, he must've tried to make a jump or something because I hear a loud sound and next thing I know he's on the ground, crying. I seriously think he's broken something. And I just keep on biking. I feel terrible almost immediately, but I do not go back.
I did tell my parents when I got home, and they have warned the kid's parents so he should be ok.

But I still feel terrible for having walked away when I saw him getting injured. At that moment I just though that he even deserved it for all years of rudeness to the whole neighborhood. 
AITA for not helping him immediately?