Hi! From your history, it seems that your testicle was inflamed initially which caused you pain with swelling in the testicle. The cause of the inflammation could be any kind of repeated trivial trauma, which has gone unnoticed by you, and
masturbation could be one of the cause. Now that the pain is no more there, probably the inflammation has subsided leaving behind a secondary hydrocele of the testis as a late sequele of epididymo orchitis. One more factor to be excluded is
varicocele of the left testis.
If the problem persists, then you may have to visit a surgeon or a
urologist, who may advise you for some routine blood tests and an
ultrasound of the testes. He may also advise you for a properly fitting scrotal support, some anti inflammatory drugs, and antibiotics if need be apart from the consideration of anti filarial drugs if your area of living falls in the endemic region of
filariasis. IF all conservative measures fail and it comes out to be a persisting hydrocele or a varicocele, he may even advise you for a surgical cure.
Wishing you an early recovery. Thanks