Awww ... the others are so right! PLEASE don't worry hun! It is perfectly normal for even the most loving cat to administer a nip now and then! As said below, it can simply mean 'enough of that, thank you meowmy', or a little love nip - did you know that gentle nips between cats (and towards humans) are similar to kisses?, or it can mean they want to play(fight)! You'll soon come to understand what he's trying to tell you
You probably spooked him more by jumping up than he spooked you! He's probably a bit confused by your reaction!
Believe me, if he meant it in anger you would have known about it, trust me!! He would have been a LOT quicker, and would likely have broken the skin - and would have used fully extended claws as well - and it would have HURT!! But that's really not likely to happen unless he gets really frightened of something and can't get away.
My little Meesh often gives me love nips, usually followed by big head rubs, whilst with Shanti it always means she wants to playfight! She's a cheeky little minx! Between cats, mutual grooming can often turn to playfighting, it's all about being a cat!
Edit: Oh just thought, a fairly reliable way to tell what he means, once he's bitten you, is to put your relaxed hand close to his muzzle. If he rubs, it was a kiss. If he grabs with paws and goes to nip again, he wants to play (you may want to train him out of this, as they will go as far as you let them!!). And if he doesn't respond, or walks off, then he's saying 'thanks, but no thanks, not just right now'. The tail can be a dead giveaway too! Twitching (or wagging) probably means either play is in order, or he's had enough. Sabby never bites, but he will twitch his tail when he wants me to stop stroking, but will often stop twitching when I rub his head instead! All part of the building communication milarky!
