The lump on the vulva
is most likely no related to PCOS
.PCOS is a hormone related syndrome which is causing the menstrual irregularities. You will need hormones to regularise your bleeding. About the lump,its possibly folliculitis
due to infection of the hair glands. Apply hot fomentation. If it doesnt burst, then you will need an examination and antibiotics. For your PCOS, see your doctor for oral hormones.