I believe it's considered self-cannibalism, but it's fairly common. Most people don't fess up to it.
I suffer from Dermatillomania, a skin picking disorder. Part of this is eating the skin you pick off. Not everyone who picks their skin does it, but most do. I do. It's disgusting and I hate it, but it's something I am not in control of at all.
I mean, as long as you aren't biting off chunks of your own flesh, I don't think it's too much of a problem. I know my disorder signals that my wiring is weird or I'm missing a few screws, but I am not compulsed to go eat other people.
I do like biting, though.