Had full toenail avulsion + matrixectomy over four weeks ago. have followed aftercare instructions. the area is slightly painful. its not infected. had this done before and they said to air wound. is keeping it covered constantly delaying healing?

No. Having it covered does not slow down healing, but, I prefer to keep it covered to protect the area during the day when you are active and keep it open at night to allow the nail bed to dry out. As for the answer to the question, keeping a wound covered actually speeds up healing because air will dry out the surface tissue and trap fluid underneath that can cause bacteria to proliferate.