Seems as though the 5 day trip in May I took to Killbear Provincial Park had some lasting effects....aside from the mental healthcare. I was bit by a Tick. It only manifested itself about 2 week...
Did you see a tick on that spot at any time ? Once a tick "latches on" it will stay on for many days even weeks. It could be some kind of spider bite.
That circle the doctor put on there is actually very important. Go over it ever few days with a Sharpie so that it stays in place. If the redness spreads, the antibiotic is nor working. You should see some reduction in the inflammation within less than a week.