Thanks for posting your query at DoctorSpring.com
I can understand your concern.
From the picture it seems to be fungal infection called tinea or ringworm mixed with secondary bacterial infection.
It will need a course of oral antibiotic like azithromycin and oral anti fungal like lamisil for sure. Oral antifungal tablets are very safe n do not make a person sick.
Application of mupurocin cream along with lamisil cream twice daily will help heal it further.
You will need a prescription for the medications.
I also would like to know if you have a history of diabetes or are there any fluid filled lesions.