Suggest Treatment For Painful Lump On Sole Of Foot

I have developed a painful ball-like lump on the bottom of my foot at the outside edge of my heel, it is hard and is about the size of the fingernail of my pinky finger. It came on pretty suddenly. I noticed the area was a little tender in the last week when I used the pumice stone in the shower, but didn t examine my foot at that time. I thought it might be a plantar wart, as I could see what resembled a pinhole center and then a somewhat white/yellow area around the center so I treated it with compound W 2 nights ago. Now I m not convinced it s a plantar wart. Do you know what it might be?