Hello,
These can be due to boils or hidradenitis suppurativa. Apply warm compresses on the lumps and keep the area clean.
Topical antiseptic treatment and topical antibiotics such as mupirocin or neomycin containing ointment is very useful.If still the lumps persist then specific treatment like antibiotics,vit A supplements,corticosteroid injections,isotretinoin,antiandrogens and sometimes excision and drainage ,laser therapy and radiotherapy are found useful.