The problem with the foot, anything to do with the foot, is that the circulation is poor down there compared to other places in the body.

I had a tumor removed from my instep and 3 plastic surgeons refused to do it saying a skin graft will not take on the foot. I was only 12 yrs old at the time.... 50+yrs ago. Today this would have been a laser procedure, but back then this hemangioma bled all the time, was very deep, and was a risk for infection.

As it was my parents found a plastic surgeon in a teaching hosp who did it. He pulled the skin over in an S shape and stitched it that way. It took over a year to heal, and now 50+ yrs later, this foot swells periodically now and the scar starts to throb sometimes. shrug? It was numb for many years, but seems the nerves have grown back and not in a good way for me.

So while the prolo-procedure may work in other places well, in the foot the inflammation might get out of hand, because the blood supply there is not good. Also being invasive, who knows?
Any thing can happen with injections, etc.

Did you try soaking in epsom salts? The magnesium in them opens up the circulation and helps with blood flow.

I find Salonpas original patches helpful for some pains I get in my feet.
They contain methyl salicylate, and penetrate locally to reduce inflammation. They are also not expensive...which is very helpful too.