I have a 1cm clear hard bump over a small childhood scar on my forehead. Is it a cyst? Should I see a derm. Or plastic surgeon? What's the cause?

Hard bump. This could be a hyperplastic or keloid scar, but if the lesion appeared years after the scar formation it is likely a sebaceous or epidermoid cyst. I would recommend seeing a general surgeon to evaluate and possibly remove the lesion.