If the toenail is subjected to direct external force, the local nail bed can be injured, resulting in local blood circulation disorder and bruising, which will have a blackened appearance. The patient can be instructed to elevate the affected limb, apply local bruising cream and take oral bone marrow medicine to improve the local blood circulation, which can gradually relieve the clinical symptoms. In addition, if the patient has diabetes mellitus, dry necrosis will appear at the end of the toe, which can also have a blackened appearance. Therefore, it is necessary to consult a doctor promptly after the appearance of this phenomenon, and the correct treatment can make this phenomenon be reduced or cured.