like others, I've been a finger nibbler for years (nails and skin around them) - maybe 40 years or so?? It's something I don't think I'll ever get rid of now and I'm well past the worst of it and can control the worst aspects (scars, bleeding, pain etc). My fingers no longer look that bad thankfully!
I'm worse when I have idle hands - driving, sat watching the TV, period of boredom etc. And like Parklife says, wearing gloves is a good way to help control it - my nails grow nicely when I'm on a skiing holiday, which gives me more to chew on when I get home!