HI. The painless swelling of the testicle ( scrotal ) growing over one year and now you are feeling it while walking. The most probable diagnosis is hydrocele, a collection of fluid in the sac evolving around testis. Another rare but more serious possibility is of a tumor of the testis itself- again a painless swelling. The best way to get diagnosis is consultation with a Surgeon / Surgical Urologist who on clinical examination , trans-illumination test using a torchlight in a dark room ( hydrocele allows the light to pass through and the scrotum glows) and ultrasonography of the scrotum and abdomen ( to see there are enlarged lymph nodes in abdomen) can tell a perfect diagnosis and further management.