Bruise/Contusion: Small blood vessels called capillaries leak blood into the surrounding tissue. This blood is either absorbed by those tissues or cleared out by your immune system.
Hematoma: Caused by leaking and pooling of blood from larger blood vessels. More blood takes the body longer to reabsorb or dispose of the blood, giving it time to coagulate (clot). This causing more discomfort and can be dangerous in certain circumstances and in certain parts of the body.
Compartment Syndrome: If a hematoma or associated inflammation is severe enough compartment syndrome can occur. CS is when inflammation in one of the bodies anatomical compartments is severe enough that blood flow is restricted to the tissue within that compartment.
RICE Protocol: Rest, Ice, Compression, and Elevation