Awww how naughty.
Oscar nips me all the time, he is very naughty.
When the Benjamin was just a young bunny he used to bite me all the time for no reason, other than it was fun for him :roll:. He used to bite my back when i was sat... and he once bit my thumb and I had a hole in the middle of my thumb for weeks. It really hurt.
Try giving your bunny treats before and after picking him up so he associates bum checks with a reward. Are there any pics of the little guy?