Or an allergic itch. In this case would be your underwear. Did you buy new underwear before this started?
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.