All kittens do this, and it's not much fun!
One thing I've found that helps is to react as another kitten would.
When he bites you, make a sudden high pitched yowl . This is what a littermate would do to let the biter know that it hurts.
This is another reason why it's good to leave kittens with their littermates until around 8 weeks - so they can learn this bite inhibition.
Your kitten will probably be startled into letting go, and then you can throw a toy for him. Catnip mice dangled on strings are good for biting, and also good for tiring out energetic kittens.