I cannot confirm anything without examination but it can be contact dermatitis or post inflammatory hyperpigmentation. The treatment for post inflammatory hyperpigmentation includes various skin creams like hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. If it still persists then you can go in for laser treatment, Chemical peeling or microdermabrasion. Avoid picking, harsh scrubbing, and abrasive treatments unless prescribed by a dermatologist during this period.
I hope it helps. Take care and please do keep us posted on how you are doing or in case you have any additional doubts. Kind regards.
My guess woud be that you are to self conscious...but that's just a guess.