A patch within the toenail that turns purple is usually a subdermal bleed, commonly seen in the big toe. There is a well-defined purple bleeding patch under the nail plate, and the dried clot can heal gradually as the nail plate grows and slowly pushes out of the nail bed. Sub nail bleeding is most common with trauma, which includes being hit by a heavy object, squeezed, or crushed. Blood pooling under the nail can cause pain, pulsation, and swelling. Painless and small traumatic bleeding under the nail usually does not require treatment, but care should be taken to avoid secondary injuries in daily life. If the pressure generated by the blood under the nail causes severe pain, decompression therapy may be used to relieve the pressure and pain by draining the blood from the affected area. The treatment is usually carried out by cauterization or needle puncture. For 12 hours after decompression, the affected area should be elevated and cold compresses should be applied as prescribed. In the case of purple plaques in the toenail with no history of trauma and frequent episodes, they may be caused by hematologic disorders such as primary thrombocytopenic purpura and aplastic anemia. In addition to bleeding under the nail, skin and mucous membrane bleeding can also be seen. Patients need to go to the hospital to improve the blood routine and coagulation function examination, and follow the medical advice for symptomatic treatment.