Subungual hematoma: This condition occurs when blood accumulates under the toenail, often due to trauma such as dropping something on the toe or stubbing it. The pressure from the blood can cause pain and may lead to the nail separating from the nail bed.

Toenail injury: Direct injury to the toenail can cause bleeding under the nail, similar to a subungual hematoma but may not always involve significant blood accumulation.
Fungal infection: While less directly related, advanced fungal infections of the toenail can lead to nail lifting and potentially bleeding under the nail due to the infection process.
Psoriasis: Nail psoriasis can cause changes in the nail, including lifting of the nail plate from the nail bed, which may lead to bleeding.

Melanoma: Although rare, subungual melanoma can present with bleeding under the nail. It's crucial to consider this diagnosis, especially if there's a change in the nail's appearance or if the bleeding is persistent and unexplained.
Infection (bacterial or fungal): Severe infections can lead to significant inflammation and potentially bleeding under the nail. Identifying and treating these infections promptly is essential to prevent serious complications.
Trauma with possible fracture: If the bleeding under the nail is due to trauma, it's essential to assess for a possible fracture of the toe, which would require immediate medical attention.

Sickle cell disease: In patients with sickle cell disease, sickling crises can lead to infarctions in various parts of the body, including under the nails, resulting in bleeding.
Antiphospholipid syndrome: This autoimmune disorder can cause blood clots and may lead to bleeding under the nails due to vascular occlusion.
Vasculitis: Certain types of vasculitis can affect the small blood vessels under the nails, leading to bleeding.