Steve ... are you 100% sure you got the tick's head out? Wife (who is very knowledgeable about medical things) says that looks like the reaction to the head infecting the bite site. It's how ticks hold on so well, they bury their heads into the skin.
For everyone, if you get a tick "in" you, and you pull it out ... be sure to use a magnifying glass to inspect the head. Be sure you pulled it out with the body.