Blood blister that hospital said was a hematoma. What does this mean?

Blood and blood. A hematoma or haematoma, is a localized collection of blood outside the blood vessels. So is a blood blister, so is a bruise but we doctors have to sound intelligent so we call that an ecchymosis. A haematoma can be huge I have seen them the size of a box turtle!
Blood under skin. A blood blister is usually due to a pinching of the skin such that the deeper tissue is injured, but the top layer of skin is still intact. A small amount of blood can accumulate under this top layer of skin and it is called a blood blister. Hematomas are also bleeding under the skin, usually due to a blow or fall. It is deeper and usually does not form a blister like swelling.