I do it too. Have been for years since teenage years. There is a name for it but i forgot what it was. google biting skin around fingernails and it will come up. I saw a bunch of sites for it so apparently alot of people have this problem. I thought it was just me. I don't know how to stop. I can't seem to help it if i see a hang nail or a piece of skin that is sticking out and catching on things i have to bite it off and it just ends up making a bigger sore. My nails will grow quite long but the skin around them looks horrible. Hope you can get some help for your sake and your childs. I don't care anymore.