Mine only tries to bite if I'm holding him. I got my first bite when he was about 5 months old.
He won't attack if I just put my hand in to clean the cage, etc. But if I pick him up to move him somewhere, and carelessly happen to get my fingers in front of his gaping (hissing) mouth, he will clamp down. And yes, it can hurt. The last time left quite a neat V-shaped cut in my finger.
Moral of the story is: don't get your fingers where they can bite. Give them space to move, and they won't feel the need to bite.