What causes a hematoma , a week later to develop again. xrays done no fracture. l hip thigh area?

Trauma: To a hematoma can cause rebleeding in the area and increase a hematoma. However, any changes in a hematoma one week after its appearance should be examined by a physician. Blood work should be done to be sure your blood is clotting appropriately. Also, a developing infection or septic hematoma can cause delayed worsening of a previously stable hematoma. See your doctor.