Hello. A bout a month ago I noticed that i have a bump like spot on my left foot right at the place of hard skin opposite to the arch and recently this bump thingy developed a crater like opening. Here is a picture
http://img31.imageshack.us/img31/9587/img2
012062700532.jpg
It hurts a lot when I walk. What is it, how did it get there and can it be treated?