I fell when running up the stairs six days ago?

I fell when running up the stairs six days ago. I caught myself on the edge of a table with the inside of my upper right arm. It bruised massively with a large bump. Bruising is healing nicely more yellow and pinkish splotches now but a golf ball sized knot remains on the inner upper arm. Will this reduce in time or do I need to have it checked?

Age: 56
Female
Medications: Levothyroxine