Hello,
I cannot confirm anything without examination, but it can be due to
Acne keloidalis nuchae. It occurs when hairs on the
back of the head and neck grow into the skin, become inflamed, and cause scar tissue. These ingrown hairs usually occur following a short haircut on the back of the head and nape of the neck.
Treatment of AKN includes suppression of the inflammation with antibiotics and steroid gels or intralesional steroid injections.