Blister on sole of foot, what to do?

That depends: On cause of blister and medical history. For example if your diabetic - see a foot doc right away and dont tend to by yourself. If healthy and an isolated blister with a sterile instrument after skin cleansed you can pierce the roof to drain the liquid. Do not remove the blister just drain then apply bandage and allow to dry out.

Blisters: Most blisters will subside on their own in healthy patients. If it's a simple blister I recommend protecting the area and if you are concerned at all with healing, get an exam!