While running a long time back i got bad blisters on the side of my big toes. they are now hard and dark underneath?

Hematoma: This is a blood filled cyst most likely (hematoma) that did not resorb on its own. They can calcify and remain permanent in some people. Depending on how long they have been there, even removal may continue to have color changes.

Bleeding blisters: Blister can get so bad that they bleed and that's what's happened. The fluid had gone out of the blister leaving a callous with dried blood under it. They will fall off in time. the biggest problem is why did you get the blisters in the first place?