I've noticed that the heel of my feet are turning the color of my skin tone..i am dark brown..and i have a sore that looks like a callous that has a h?

Foreign body: If the callosity is coming to a head, you have a foreign body that is being extruded. If the "callus" id painful and on the sole, it would be a plantar wart. This needs careful removal of all the thick dead skin until you can see tipping dot in the middle. While the core is exposed let a dermatologist freeze it with liquid N2. Not concerned about the pigmentation. Brown is beautiful!!