A patch within the toenail turns purple, usually in the presence of a subnail hemorrhage, commonly seen in the big toe. There is a well-defined purple hemorrhagic patch under the nail plate, and the dried blood clot can be pushed out of the nail bed slowly as the nail plate grows, thus healing gradually. Subnail hemorrhage is most commonly caused by trauma, which includes being hit by a heavy object, crushed, or crushed, etc. Blood pooling under the nail can cause pain, throbbing, and swelling. Painless and small subnail hemorrhages caused by trauma usually do not require treatment, and care should be taken to avoid secondary injuries in daily life. If the pressure from the blood under the nail causes severe pain, decompression therapy can be performed to relieve the pressure and pain by draining the blood from the affected area. This is usually done by cauterization or needle puncture. For 12 hours after decompression, the affected area should be elevated and cold compresses should be applied as prescribed by the doctor. If there is no history of trauma and frequent episodes of purple plaques in the toenails, they may be caused by hematologic disorders, such as primary thrombocytopenic purpura and aplastic anemia. In addition to subnail bleeding, skin and mucous membrane bleeding can also be seen, the patient needs to go to the hospital in time to complete the blood routine and coagulation function examination, and follow the doctor’s instructions for symptomatic treatment.