Most skin ringworm (not actually a worm, but rather a fungus) infections in children are easily treated with an over the counter anti-fungal cream, like Lotrimin. Yes, I do mean the athlete's foot cream.
If the fungal infection is on the scalp, usually an oral anti-fungal medication is needed. This is because the skin of the scalp has a thicker keratin layer and the creams and ointments have a harder time being absorbed enough. In babies, you should just use the anti-fungal cream or ointment because their keratin layer of the scalp is not as thick and we avoid the oral form of medication.