That sounds like Lyme Disease. You need antibiotics. See a doctor.
What's A White Dot In The Middle Of A Red Circle On The Skin?
It could be many things. Is there a cut or a red irritated area within the circle.? It could just be a diaper rash. Where has that skin area been? I can remember getting something like that under my watch when I had been snorkeling. But without more info, I can't tell you much. Just go see the doctor.