A recent onset of a pigmented spot on the scrotum
should not be ignored.Its always get it evaluated so that the doubts are cleared.
A long standing mole or pigmented lesion which recently has changed in colour/size/shape/painful is also a cause of concern.However presuming that the lesion you are mentioning is of recent onset i would recommend your boyfriend gets examined by a dermatologist/surgeon.A biopsy
may also be indicated.
All the best