Gum Abscess or Canker sore?

On thursday of last week I went to the dentist for my yearly check-up and during this visit my teeth were examined and cleaned. Once the cleaning was done my dentist told me that my x-rays showed no cavities and that my teeth and gums were in pretty good shape! I also didn't have any signs of tartar build-up or problems with bleeding gum prior to my teeth being cleaned. A few hours after leaving the dentist my mouth felt sore and my gums felt slightly tender and swollen. A few days later my gums still felt tender and swollen but I was also starting experience a slight stinging and burning sensation. When I looked in my mouth I saw that I had a red bump directly on my gum near my tooth in the back. The bump itself is somewhat raised with tiny pimple like spots that have pale yellow-white centers. This bump has been very painful especially when I eat and brush my teeth! My guess is that I have a really big canker sore however, I'm not exactly sure because I've never had a canker sore on my gum before and I've also never had a gum abscess. Is it possible to have a gum abscess even if I don't have any dental cavities and have never had any problems with my gums? I plan to call the dentist in the next few days if I'm not feeling any better. Your help is greatly appreciated thanks a bunch!