Are you sure it was a tick and not a brown recluse spider? The spider creates a distinctive 'bull's eye' mark. One of the leaders got bitten by one at the Girl Scout town encampment, and it left a nasty mark.
Yah know... just a few weeks ago I got a bite of some kind. On my back, or really on my side about even with where my elbow hangs. It was just a big red bump, maybe 3/4inch in diameter. No circles or anything.
I figured it was a spider... and it has since all but disappeared. But it was too big to be a mosquito or anything else I've seen.