Hematoma is commonly caused when large blood vessels are broken, from broken bones or trauma, causing pools of clotted blood to gather deep under connective tissues and muscle. (Taneja, 2010)

It can form on any parts of the body, such as in the head, fingernails, under the skin, ear, septum of nose, muscles, stomach, and many other parts of the body. This is different from bruises which generally appear under the skin and hematoma can form on organs and tissues. (Quinn, 2023)

Depending on the size and location of hematoma formations, it can heal on its own or require medical attention if it affects vital organs. (Quinn, 2023) 

Unlike bruises, which are appear flat underneath the skin, hematoma formation forms raised bumps due to the accumulation of blood clots. It may feel spongy, rubbery, or lumpy and may appear red or purple. (King, 2023)