It does not sound like cancer, which would be a solid mass that is part of the testicle and would have grown by now. It could be a cyst or a hydrocele, which are liquid filled and generally could be pushed around independently of your testicle. I suggest you get an appointment with your family doctor and urologist for a complete exam and ideally a scrotal ultrasound for a definitive diagnosis. An ultrasound is a painless scan with a transducer just like the ones used to check on a baby's development in the womb. The things I mentioned rarely need treatment and are better left alone since "over-examining" can cause irritation and swelling.
Let us know how it goes, and best wishes.
"Statistics are human beings with the tears wiped off" - Paul Brodeur
Diagnosis: 05Sept07 Right I/O: 13Sept07; Pure Seminoma; Surveillance only per NCCN: All Clear February2013 (Chest Xray, Markers); Next check August2013 (CT Scans, Markers)