My son has a circular rash on the bottom of his foot (about the size of a dime). When he first showed it to me the inner part of the circle had almost a blister/burn look to it with a darkish red ring around the edge of the cirlce. 2 days later it is just the red ring, some of which has a pin point appearance other is just solid, slightly raised. The reddish color is starting to fade now, skin in inner circle looks normal with no blistering. Wondering what it could be. We are in the middle of tick season and they seem to be very heavy this year have killed several that have been brought in the house by dog and kids after hiking.