Pea-sized lump in groin area. not sure how long it was there?

Pea-sized lump: The most common pea-sized (3-5 mm) lump in the groin area is an ingrown-hair which blocks up a hair follicle and enlarges as normal gland secretions can't get out. These will usually take care of themselves, as long as the hair follicle itself does not get infected from the irritation, in which case an antibiotic would be indicated. Another possibility is a lymph gland, but these are usually large.