It looked like Nevus Sebaceous initially, but could be naevus comedonicus. so have you had any lesion when u were child ( when did ur mom popped,..age).Does it have any sensation now, pain, itch, burning/tingling? How old are you?
You may apply antibiotics or take oral antibiotics if u suspect any infection. Although several treatment options are available, surgical excision is the best option. Most importantly in case of inflammatory type, repeated bacterial infection is very common.
Being said that diagnosing online just by the pic is hard, direct visual examination is very necessary in most of the skin condition. SO i would suggest u to visit the dermatologist and confirm the case ( in some case biopsy may be required) and treat accordingly.