I think what is on tho bottom of your feet are called planters warts. I had them a long time ago, when I was young and a foot doctor helped me get rid of them. I don't remember how. Here are some links that I hope will help:
http://www.montana.edu/wwwhs/medserv/wart.html
http://www.lib.uiowa.edu/hardin/md/plantarwarts.html
Mark