Hi ! From your history, it seems that you have got a small hydrocele
possibly due to inflammation of the testis along with epididymis
. This can occur due to un noticed trivial trauma of the testis, or due to any infection may be along with a UTI. Now that the inflammation might have subsided, some fluid might have got accumulated as an after effect of the inflammation. It may get subsided with some anti inflammatory and antibiotics drugs. However, if it does not, and goes on increasing in size, then you may have to consult a surgeon who may advise you a surgery which will relieve you of the condition. Wishing you an early recovery.