If only the skin was hurt, treat it like any other wound. Make sure to dry it thoroughly after washing, and do not rub it - rubbing the skin allows bacteria to enter. Just wash gently, pat dry, and apply antibiotic cream. If it gets worse - becomes redder, or more swollen and tender, do see a doctor.
These tips might help: https://www.aad.org/public/skin-hair-nails/injured-skin/minor-cuts