excoriation disorder / skin picking
Also called dermatillomania or excoriation disorder, skin picking disorder is where you cannot stop picking at your skin. There are things you can try to help yourself, but some people may need professional treatment. Skin picking disorder is related to obsessive compulsive disorder, where the person cannot stop themselves carrying out a particular action.
It's sometimes called a body-focused repetitive behaviour and is similar to repetitive hair pulling disorder (trichotillomania). It's also related to other obsessive compulsive disorders, such as body dysmorphic disorder, where the person is excessively preoccupied with their appearance.
People with skin picking disorder often also have other obsessive compulsive disorders. These may require their own assessment and treatment.