What could a bone-like lump on foot be?

I found a hard bone-like lump on the top of my left foot a couple of months ago. It was painless at first, but as time passed, pain started occurring. I work in retail and I'm on my feet all the time and its just getting worse and worse. One time I came home and I could barely walk and the pain had reached up to my knee. My entire foot was swelled up, tingly, numb, and in horrible pain. Any idea what it could be?