Why won't my hematoma go away? what should i do?

Apply warm soakes : It will go away in time. Hematomas are collection of blood in soft tissue due to injury, or result of invasive procedures most of the time they will resolve on their own , not the blood clots that cause embolism, need to drain & evacuate if they are pressing on a vital structures, or huge , drainage or even aspirations , has potential danger of getting infection.