My bf has a perfect bald circle maybe 3-4 in diameter. will not grow hair back in that spot. any ideas on what it could be?

Bald: More often than not the bald spot is very common in men, particularly as they age, even from about 25 on. A dermatologist would be the right person to address.

Patchy alopecia: That particular small area has damaged hair follicle. If more areas develop may need work up for diseases that could cause alopecia or medications.

Alopecia areata: Will grow back in time. May be many months. Avoid rubbing too much. Can try minoxidil. Clobetasol gel (prescription) may help. No reliable therapy but will recover in time.