Disclaimer: I have not been diagnosed with OCD, although I suspect it. Feel free to disregard my advice.

I used to bite my nails and bite off the skin around my fingers until I would bleed. In the last 6 months, I’ve stopped completely.

First, I replaced actual biting with just putting my nails in my mouth, so it felt almost the same to my muscle memory and my impulses but not quite. Maybe for skin picking, when you have the impulse to pick, you can put your hands on your skin but not pick or peel. You still almost satisfy the impulse, but you don’t harm yourself.

Eventually, I stopped putting my nails/fingers in my mouth completely, and now for the first time in 10 years I have healthy nails.

I hope this helps!