Yes Please. I Have A Rash That Has Formed On

Yes please. I have a rash that has formed on both of my valve muscles and back of both ankles. This is the second time this has happened in two weeks. Both after walking anywhere from 10-20 miles. It only burns when I'm using my valve muscles. I was wondering if I should be worried or get help ASAP. Plus I was hoping you could tell me what it is???