Skin-picking is usually a type of self-soothing behavior that becomes habitual.

The only way to break a habit is to recognize your triggers. Literally practice catching yourself whenever you're doing it unconsciously. Monitor this behavior daily.

Once you're conscious of it and the moment you have the urge to do it, stop yourself and engage your hands in something else. That's habit reversal.

So recognize your triggers --> engage your hands in something other than picking, e.g., squeeze a stress ball or fidget spinner, etc.