Should I see a dermatologist or a podiatrist if I have some kind of fungus on my foot?

It's not athletes foot, or a nail fungus. It's causing the skin on the bottom of my feet to get hard, scale and crack. I've tried all the over the counter ointments for the past 6 months and none work. I keep using a ped-egg to keep it in control but it's getting worse (spreading), but it's not contagious cause my other foot hasn't gotten it, nor has anyone in the house.

Should I see a Skin Doctor or a Foot Doctor?