It sounds like it could be the infamous bull's eye rash. It occurs when a tick bites you and if the tick is a carrier of Lyme disease then later you will have neurological symptoms. Your muscles will twitch, you will lose control of all muscle movements, equivalent to seizures. There are pictures of it on google and I would suggest you go to the CDC. gov, it's the center of disease control's website. Seriously this is not something you want to take your time on. Lyme disease is showing up quite frequently all across the United States and sadly people have loss the ability to perform everyday functions because of this. You need to see your doctor and they need to start treating you immediately.
On the other hand, it could be ring worms. It's not really a worm just a fungal infection.
Tinea pedis: Athlete's foot may cause scaling and inflammation in the toe webs, especially the one between the fourth and fifth toes. Another common form of tinea pedis produces a thickening or scaling of the skin on the heels and soles. This is sometimes referred to as the "moccasin distribution." In still other cases, tinea causes blisters between the toes or on the sole. Aside from athlete's foot, tinea pedis is known as tinea of the foot or, more loosely, fungal infection of the feet. Tinea pedis is an extremely common skin disorder. It is the most common and perhaps the most persistent of the fungal (tinea) infections. It is rare before adolescence. It may occur in association with other fungal skin infections such as tinea cruris (jock itch).
It's highly contagious and you don't want to spread it to other people. Wash and sterlize everything.
Either way you need to go and see a doctor becuase the doctor can prescribe the medication you will need to get rid of your ailment.