You can post a picture on your profile page. :>) I'm thinking, though, from your description that this sounds fungal in nature. Good times. Athletes foot can grow on the top of your foot. It doesn't itch at all though? Here's a medhelp doctor on a similar post saying it sounds like a 'bite' and to see a doctor. https://www.medhelp.org/posts/Dermatology/small-red-circular-rash-on-foot/show/244622. Kind
of wonder about a tic bite? The bulls eye that comes with lyme disease is a bit slow to develop?
But it does sound also like ringworm to me. Read this and see what you think https://www.webmd.com/skin-problems-and-treatments/what-you-should-know-about-ringworm#1
I think it's best to see the doctor at this point for an accurate diagnosis.