Me too :( thumbs mostly. Gets worse in cold weather like this, agony and very embarrassing. I notice I have been doing it more if stressed, even if I didn't realise something had upset me, my fingers will tell the tale.
I would like to stop doing it before my children think it's ok to do it too! Bizarrely I am paranoid about germs and hand washing so as not to pick up bugs, yet I can't seem to stop nibbling myself (and yes I do most often eat the scraps).
Is there a name for this vile habit? I don't know anyone else in real life who does it.