Is Epididimal Cyst On Testicle Serious?

I have a lump which is actually on one of my testicles, i got it hecked by a doctor who said he was confident it was an epididimal cyst. It is very small, i would say 3mm roughly and theres no pain. He said to ease your mind you can be send for an ultra-sound but said how about leaving it for six weeks to see any developments if your still worried. He said its all fine but come back if there are any changes like it getting bigger. Its been a while now but in the back of my mind theres the what if question. There have been no developments and everything is exactly how the doctor saw it. Is there any other opinions out there?