I was standing barefoot cooking dinner last night and suddenly noticed that the arch of my left foot was hurting. I took a look at the bottom of my foot and noticed a bump underneath the surface on the inside upper portion of my arch, the size of a quarter, and it was already bruising. By the time I went to bed, about 3 1/2 hours later, the bump had significantly gone down... however, I've been left with a bruise about 1 inch wide and about 2 inches long... and although the bump has not come back... it's very sore. What in the world could have caused this spontaneously to happen? And what, if anything, should I do to help it heal?