Fingernails cut a slit by a knife should be immediately rinsed and sterilized, bandaged to avoid contamination of the wound, and urgently treated in a hospital. After this happens, the wound should be rinsed with water to remove the foreign matter in the wound, and then sterilized with iodine vapour, bandaged with a clean band-aid to avoid contamination of the wound, and go to a professional hospital for further treatment by a doctor. If the wound is small and the bleeding is not serious, after the doctor has treated the wound with local bandages, it does not need special treatment because it has a certain self-healing ability, but you should prevent the wound from getting infected. If the wound is deeper, injuring the nail bed, and there is a tendency of infection, then the doctor will do nail extraction according to the situation surgically. After the operation, you need to change the dressing regularly and take antibiotics such as amoxicillin to prevent infection. Nails cut a slit by the knife should be timely to the hospital to avoid self-treatment caused by adverse consequences.