Besides ringworm what kind of rash can cause a red circle with a wart like skin tag on the breast area? it showed up over night

Many things: Here is the list - pityriasis rosea, eczema, pyogenic granuloma, etc. Skin issues are difficult to diagnoses without seeing them - if it persists, seek care.

Possible infection: Redness with a centrally raise area could be staph infection with acute onset. Since if this infection it could invove deeper breast tissue it is nest to e treated with antibiotics. See physician for proper diagnosis and treatment. If infection spreads to deepr tissue it amy result in scarring and potential future problems with mammography.

Red/Circle/tag???: Nit sure? Bed Bug bites a guess. Best to seek in person examination from a doctor..