Tiny jaws of doom

I'm trying not to take it personally, but Vodka has taken to biting me, quite literally the hand that feeds him, and cleans out his cage, and provides him with toilet paper for shredding and every other possible comfort a tiny rodent might want.
He bit my palm just moments ago when we were having a nice, calm little chat, I think because he was startled when the phone started ringing. I dropped him in his playpen (a plastic bin lined with wood chips and appointed with wooden shapes to climb on and plastic tunnels to walk through) for a cooling off period -- after I had given him time to let go of my skin. When he sinks his incisors into me, it's not just a momentary nip, he hangs on until he feels the danger has passed. He draws blood and leaves tiny gashes in my skin. It's really painful.
Now he's circling his playpen, occasionally pausing to chew on his little wooden jungle gym. He has a victorious air. Every time I lean down to check on him he stands on his tiptoes, front paws held in front of him in a protective fashion, and sniffs the air as if to say, "Oi, Scary 50-foot Woman! Come any closer and I'll bite your big stinky nose. Don't think I won't -- you've got my dander up now." He's clearly excited and pleased, possibly recounting our skirmish in his mind and making plans for the next.
I'm not sure what to do about it. This is the fourth or fifth time Voddy's bitten me in the past two weeks. It's rapidly becoming a habit of his. While Lime is a placid, and probably not particularly smart little fur ball, quite happy to sit on my lap and eat treats from my hand, Vodka is determined to make our relationship difficult. I am hesitant to put new food in his cage cos he attacks my arm, and taking him out for a run in the exercise ball seems like more trouble than it's worth. It is ridiculous, but I am scared of my three-inch dwarf hamster. No wonder he looks so smug.