After reading your history it appears that you might have developed allergic dermatitis
to some contact allergen or ther emay be possibility of eczematous lesion also.
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
You can go for skin biopsy
of the area so that exact diagnosis can be made out.