Jeez, I don't know. My cat, Loki, does the same thing with my ring. I just figured he's really playful(/annoying!). He also bats at my necklace, tries to chew on buttons and the necklace. When I adopted him I was wearing my necklace and my sister was wearing a shirt with buttons, which he took turns trying to chew on, yet I still took him home! He also likes to try to chew on my glasses. I just make sure I keep all these things put away where he can't get to them. Unfortunately, once I didn't put my glasses away and I woke up to one of the ends chewed. Moron.
He's over 2, too, so it's not him being a kitten. He's just bitey. Sometimes he likes to chomp down on me (not very hard). He likes to bite my feet and my toes, which I'm not particularly fond of, so sometimes I have to watch him. It's not him getting over-stimulated, either; sometimes he's just a little jerk!