Sores and blisters. Ringworm infections very often create blisters that erupt with pus. The liquid will often form a crust that will develop into a hardened or scale-like skin. The area at this point will shed flakes, and itch severely, and be quite tender as well. This usually occurs between the digits, but it could also happen on the sole or on the sides of the feet. Generally speaking, blisters of this sort do not form in the upper region of the feet.