Large pimple on neck, usually get one at a time. is this just a large pimple or a form of cystic acne and how can i control it?

Acne: Without seeing it, suggest you just keep clean and use a topical anti- acne cream. If it gets infected see your doctor.

Cyst: Acne can present as large cyst like spots but usually in more general areas. Some cysts are sebaceous, caused by a plugged up oil gland. Some could be infected sweat gland. Sometimes infected with staph. Should get your doctor to see this to get the correct diagnosis.