I have a black painful sore between my toe. its painful to walk.

See: a podiatriast. Description may suggest need for debridment

Biopsy?: Hi. I've seen more than one patient with melanoma in the toes. I suggest you see a doctor and see if you need a biopsy, or if something else of significance is going on. Good luck.

Best Seen.: Without seeing the area, it is difficult to be sure. It certainly could be either a wart with blood underneath it or a callous with blood underneath it. Either way, the resolution is to have the area evaluated by a foot specialist.