Hi Doctor, I have off and on been experiencing blister like area on just one foot that are sometime painful, wake me up at night, become large, not from any friction or running, come and go look like they can be filled with a yellowish substance at times, come in various sizes and shapes do not itch then they are gone and leave a dull grayish small dry spot, but if I try to make a doctor appointment they are gone, I have one now that is growing to the size of about a quarter that started during the night last night, any suggestions>