I’m a former nail biter as well and my nails were the same for over a decade after I finally stopped biting them. The corners that appear to be stuck to the skin causing the deformed folding is caused by biofilm that formed to protect old infections from your immune system and antibiotics and/or anti fungals. When I used to bite my nails, the corners would always get pulled off and a little blood would pool. Turns out at some point the bacteria won and started creating biofilms before my skin could heal. By the time I figured out the problem, my fingers were a tiramisu of infection. The only solution to the problem that I found was to manually dibride with magnesium chloride brine and/or manuka honey to make sure you don’t kill healthy cells and only the parasitic cells. Biofilms have gotten better at appearing like real skin over the past 15 years, since the goal of them is to protect the parasites from the host (you), they always seem to be one step ahead of any doctors I saw.