A hematoma is a blood leakage outside a blood vessel when blood spreads in the tissues around. It can be small as a dot or rather big, it swells and hurts.
1. A hematoma is a result of a long bleeding when the blood clotting is insufficient and the blood comes out of the vessel (it can be capillary, vein or artery). The cases can be complicated with strong leaking due to the blood pressure inside the vessel like in a major artery.