Thanks for your query.From what You have mentioned it looks that your testicles are normal in size and there is no pain in testicles.It is likely to be a skin infection
of the scrotum
mostly due to fungal infection
which in it turns is secondary to your inner wares and bad hygiene.. Please wash your inner wares in hot water mixed with dettol
solution.Apply Mecanazole ointment( Zole or Daktarine) twice daily after cleaning and washing scrotum with soap water twice daily.It should be fine within 4 days.