Is this ulcer normal?

5 weeks ago a VERY PAINFUL ulcer appeared on my gums, the border was white and thin, and 2 weeks ago the pain seemed to have stopped, and the ulcer became less noticeable, and the border thickened. TODAY, it is sort of still there, but you have to really look for it to see it. Its not as noticeable, there is no more pain. If i were to measure, the ulcer was about 6-8mm in diameter.. Is this cancer or scarred tissue?