if you search online for
bullseye rash pictures
you will find lots of photos that have a remarkable variety of how red, how big, how circular, how disk-shaped, etc etc. There is not one single presentation of a bullseye rash, and if I got anything remotely looking like any of those shapes, I would take a photo of it and get myself and the photo to a Lyme doc asap, just in case, and the sooner the better.
When you click on post a question and it comes up for you to type they question and title, there should be a post photo link just below.