I would strongly recommend that you see your primary care doctor
. Pending his or her evaluation, a dermatologist
(a skin specialist) may be helpful.
Rashes or skin changes on the soles of the feet are actually quiet unusual. There is a small list of things that effect the palms and or soles. The first to always consider is a skin cancer, specifically melanoma. Melanoma on the palms and soles is known as acral lentiginous melanoma. It is not that common, but more seen in people of dark skin color (African Americans and Asians). Generally speaking, a biopsy (looking that the skin under the microscope) is the only way to definitively rule this out. This cancer can spread and therefore requires early evaluation.
That being said, it is more likely that you have a benign (or less troubling) cause. The most common cause is friction blisters that can occasionally develop blackened color (as skin pigment cells get involved). These sometimes require debridement (removing the dead skin cells) which can be done by a podiatrist
(a foot doctor). Other causes can included viral infections as well as an occasional bacterial infection.
I would recommend seeing your primary care doctor. Cutting them yourself risks infection and therefore I would not recommend that approach.