Hello,
Without examination, confirmation of a diagnosis is tough but it can be folliculitis, cysts , epididymal cyst(found inside the testicles) or genital warts(caused by HPV infection).
Apply warm compresses, Neosporin ointment and calamine lotion and avoid messing with it. You can take anti-inflammatory pain killers like ibuprofen or acetaminophen. If the lump persists then it will be best to get it evaluated from a dermatologist.
I hope it helps. Take care and please do keep me posted on how you are doing or if you have any additional queries. Kind regards.
Or an allergic itch. In this case would be your underwear. Did you buy new underwear before this started?