Subungual melanoma and subungual bruising have different causes and different symptoms. 1. Causes: The causes of subnail melanoma are not clear, usually related to heredity, race and immune function. Subungual bruise is usually caused by trauma or extrusion of the local tissues of the nail congestion, patients will experience local pain and swelling. 2. Different symptoms: subnail melanoma will appear black or brown pigment bands, stripes, splints will appear cracking and thickening and other symptoms, with the development of the disease, the affected area will gradually increase in size. Subnail bruises are usually accompanied by localized pain symptoms, while the affected area will appear irregularly shaped dark red spots, the border is clearer, usually does not last too large. Patients with subnail lesions should seek medical attention in time to avoid delays.