The symptoms are suggestive of some type of infection, too non-specific though to make a specific diagnosis without looking at the rash
and conducting a physical exam. Depending on your location, one can consider tick-borne diseases such as Lyme, that can have flu-like symptoms and a red bulls eye round lesion.
My best recommendation will be to be seen by a provider who can assess the rash and send basic preliminary tests for infection.
Dr Brenes-Salazar MD
Mayo Clinic MN