my copper delta, Dante, is horrid about biting his own tail. it's not always an easy fix, and the main thing is to figure out WHY he does it. with Dante, i noticed, he only bit his tail when i'd leave my room for hours, making me think that maybe i was his entertainment, and without me, he got bored. so, i added more plants to his tank, and re-arrange everything at every water change. it keeps him entertained and happy now, because he has many plants to hide in, and things are always interesting for him. since i started doing that, he's not bitten his tail once. :3
so, for your boy, try to figure out if it's stress, or boredom. try adding more plants, be they live or silk, and some hiding spots, like caves or even coffee mugs, so he can hide when he feels stressed. to help his fins heal up, i dose with aquarium salt at first, to keep infection away, and add an Indian Almond Leaf to help his fins grow back.
hope i helped. :3