Put obstacles between yourself and whatever implements/room you use. Also consider what soothing mechanisms you can use instead when the habit kicks in.

Your emotions make sense, self-harm isn’t rare, but pulling off your toenails really is a bad idea. Even if you feel relief from the pain you are still making your body more fragile in the long term and risking infections in the short term.

Good job asking for help at all, now please find medical help as soon as you can. Don’t let this issue fester.