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. So apply antibiotic cream like Neosporin or bactroban. If the symptoms persist then oral antibiotics and steroids may be needed. Please consult a dermatologist in that case.
Larger bumps of AKN present for a while or if not responding to treatments may need surgical removal.
I hope it helps. Take care and please do keep me posted on how you are doing or if you have any additional doubts. Kind regards.