Testicular Cancer or Cyst?

when i was about 17, i noticed a little lump on my right testicle and i thought it was cancer. i got it looked at and my doctor said it was just a cyst and not to worry. i still have a lump and im now 20. it doesn't hurt and it just swells up every now and then. its more toward the upper front of the right testicle towards the epididymis. should i be concerned again? is it possible cancer? please help...