cyst on gum

I have had a cyst on my gum for about a year now. I thought it was an abcess (abscess) but I went to the dentist a couple of days ago and he said it was a cyst. When I first noticed this cyst (above my right front tooth on my gum) it was filled with pus looking stuff. I didnt know what it was. I also noticed that my right side of my neck was swollen a little. I had pain in my right nostril above the cyst. I often wonder if this is really a cyst. My dentist didnt really take a close look at it he just glanced at the cyst and the xray and he said it was an abcess (abscess) at first then he said it was a cyst. How can I get rid of this and how do I know this is really a cyst? Every morning when I wake up, the cyst is filled with pus looking stuff and it bursts quit often. This is gross. I have looked on the internet but I cant find any information about cysts on gums. Can this be cured with a root canal?