Sounds like you busted the servo. Go to your local hobby shop and pick up a new servo. Cheap ones like the futaba 3003 are about $15 and you could spend up to 150$ on a race worthy servo..
Servos are pretty tuff but if you hit curbs you will brake them. For about 30-40$ you can get metal gear servos that will take a little more of that abuse..
Try your best not to hit curbs though