Foot crater

Hello, sorry if this question has been asked before. I tried making searches with similar terms, but have found nothing of use.

Three or so years ago I started playing football (hard surface, astro trainers). First it was once a week for an hour, then after about a year it was twice a week, and has been ever since.

When I first started playing frequently a blister formed on the ball (big toe side) of my right foot. It was probably about an inch in diameter. The blister never went away and I just played through it. What seemed to be happening after a while was that a crater was being dug into my foot - after ever game I could see a new layer of skin, as well as the broken edge of all the old layers.

I was hoping that eventually the skin would join back up again, but this never happened.

The skin is much harder and tougher now, but it is not continuous. I have what appears like a sort of ulcer on the sole of my foot - but with hard, dead skin and little pain. It is a couple of square centrimeters in area. The "sides" are living skin and instead of joining and growing back over they actually seem to grow "up" forming a kind of ridge. In the middle a big, very hard knob of dead skin and other random debris grows up, totally separate from the sides.

I have tried filing this whole lot down with a pumice stone, but I can never make it totally flat. After a couple of days the living skin around the sides grows up again and the whole thing starts to take on the "ulcer" like appearance again.

Anyhow, sorry for the essay. I tried to describe the whole issue as succinctly as possible.

Thanks in advance.