My 19 Yr Old Son Was Clearing Trees And Brush

My 19 yr old son was clearing trees and brush in Georgia this week. He pulled 16 ticks off of himself. Some of those spots have a blister. Other places have sores about the size of a nickel with a bit of pink and swelling to them. No "target" look to any of them. Some are reacting well to ointment. While others seem to be festering. What could this be and how shall I treat it?