I recently contracted traveler s diarrhea and experienced a particularly nasty bout of it. Burning and very little eating made it particularly painful. I developed a small sore right next to my anus, it isn t very painful now that I ve gotten over the infection, only when muscles are tightened. It s about 1/4-1/3 inch diameter and is soft to the touch, but too firm to feel like puss to me. Is this a bacterial cyst?