Head Racquetball Gloves How Do I Get Rid Of This Lump On My Head?

How do I get rid of this lump on my head? - head racquetball gloves

There are about 4 years ago I met the head with another player during a football match, while we both jumped for a header. A hen's egg on my forehead / temple immediately appeared on the size of a tennis racket. I went to the hospital they told me it was okay. But I still have great quarter hardening on my forehead. It hurts, I did not get a headache, just ... no. What is it and I can get rid of it? Calcium deposit?
Thank you!