I fell about 2 years ago and bruised my thighs very badly. Once they started healing these growth type pockets that are very red and painful started to appear on the injury. I pressed hard on them and they popped under the skin. They never came back until 5 days ago one appeared on the same spot. It's growing fast but I can't seem to pop it when I press on it. It's about the size of a nickel. What is it???