Get this problem taken care of as soon as you possibly can. And get tested for diabetes. You want to keep your foot!
A former coworker of mine was diabetic (and an alcoholic - as you can imagine this story won't end well) and he got a bruise on his foot from dropping a bigass Folgers can on it. That turned into an infection and he didn't manage it very well. Over the next two years they eventually shortened his leg up to the knee in about 4 different increments. He died of other diabetic-related causes a year ago.