After reading your history it appears that you might have developed dermatitis
to some contact allergen or due sweating. I advise you to not pinch or pop the area otherwise these areas are very prone for getting secondary infection. You can apply an steroid cream such as cortisone
cream. If itching is present then can take benadryl accordingly. Apply a plenty of moisturizers over the affected area. If these increase then consult a dermatologist
for higher treatment. If the infection increases then oral antibiotic like ciprofloxacin
can be taken under medical advise.