Thanks for writing to us.
From the description provided firstly you need to rule out whether the cysts that you have mentioned is recurrent boils
or the lesions of hidradenitis
suppuritiva. For the same please consult a dermatologist
As far as chaffing around the pantyline is concerned, it is due to intertrigo
Application of an antifungal steroid cream combination should help in treating the area.
It doesnot seem to be MRSA infection
Hope that helped.