Chews white dot on back?

by Maddy LeClair
(Rochester, NH, US)

I received my pet parakeet 3-4 years ago. He is a bugie and he has a white dot on his back. He has had it for awhile and he keeps chewing it. at first i thought it was a feather, but it is just a dot.. he has now chewed his back and it has almost no feathers in that area. sometimes it even bleeds. i dont know what it is or what to do.. please help!