Hydrocele is a collection of sterile fluid in the cord attached to the testicle, which is invariably harmless. Left untreated, a hydrocele can grow to a large size (even a football) and cause discomfort.
It can be demonstrated by shining a flashlight (transillumination) through the enlarged portion of the scrotum. If the scrotum is full of clear fluid, as in a hydrocele, the scrotum will light up unlike a tumor which being a solid does not light up. An ultrasound may be done to confirm the diagnosis and is one of the best tests. I suggest you to consult a general surgeon and get done these tests to confirm the diagnosis.
If it is a hydrocele it has to be drained surgically.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.