Before the blister form, you'll feel uncomfotable from your foot just like a sand is there or sock is not in the right position. If you are not in a race, stop at once and check, then the blister can be avoided. In a race, it is difficult to make a decision, never try anything new, shoes, sock or even a new pair of shoe laces.
When a blister is there, the only you can do is just wait. A few days for its recovery and no short cut.