3 small bumps (cysts?) on the back of head, best way to treat?

Cyst Treatment: If they have been there for several months then they will probably need to be surgically excised. If new (less than a month), they could be acne or folliculitis and might respond to a steroid injection or oral antibiotic.

Bumps on scalp: most likely this is ingrown hair follicles--i would do normal hygiene on scalp--consider topical antibiotic ie neosporin--but may need to see your doctor for the possibility of an oral antibiotic