It seems that you may be having acne keloidalis
They are acne like lesions occuring on back of the neck.
The disease occurs fom hair follicle.
There may be scarring like keloid.
Application of retinoic acid
gel in low strenght would be helpful.
10 mg daily at night and cap. minocycline
50 mg daily in morning for few months may be taken.
Intralesional steroid injection would enhance the recovery.
Stress can increase your disease,so avoid stress.
I hope you got my answer.
Dr. Ilyas Patel MD