I have an unexplained greenish/purple bruise that really shows purple dots all around it. The circumference is about 2.5 inches and it has a tiny bump/cyst like lump in the middle. I can feel the tiny cyst. There does not appear to be an opening for it to be a spider bite. I have not injured myself. I do jog about 3 days a week but have never experience this before. What could be the cause of this?