Actually, at his size, he might just be hungry. My pastel chewed on me non-stop for the first two days I had her, ate two mice on the third day, and hasn't bitten me since.

But yeah, about 20-30% of hatchlings are nippy, or hissy, or neurotic. Almost all of them grow out of it in 6 months to a year. Usually the nippy ones are good eaters, though!