Test nibble to see if he could eat you. Turning their head in and biting or advancing with a full body slither, maw gaping, are simply "i'm going to eat this" food moves. I have never in my life seen a proper, open mouth, strike from a hognose. They'll huff and puff a bit and do a couple feigned(closed mouth) strikes but if this doesn't work they'll do their darnedest to retreat or play dead.

So, to answer your question, they are not nippy in the normal sense of word. They are a bit mouthy though, as they are very food oriented little critters. This just means you need to pay special attention when working with them until you learn their individual habits or "train" them out of thinking your digits are food through regular handling sessions.