Several years ago it seemed like I had a cut across the bottom of my foot along the top of of ball of my foot. Tried everything and it got no better. Starting watching Isomers after reading all the comments here on the board. First thing was to change soaps use only Isomers which is ph balanced for the skin and started using the Cooper P and the Redensify and it healed it.
Don't let the people scrub or pumice your feet, soak in their soaps or use their lotions.
eta - I agree with other posters stopping the pedi's.. So many are addicted to that and mani's - totally understand but never got into that as much as I love the look.. Grease or vaseline won't work on it and cotton absorbs more moisture away. It could be your nerves, psoriasis, eczema or just an allergic reaction. Many get it on their feet only. Excessive pain like you are saying is something that should be address so you don't make it worse and seeing any dr or nurse assistant may give you immediate relief physicallly and mentally.