What could be the cause of gum pain about 2 months after a crown is installed?

I had a crown installed at the end of August because of a broken tooth that was mostly filling. I was very shocked and concerned when the dentist numbed the area around the tooth because of the amount of pain and discomfort I experienced.  Around 3 weeks ago, I started having a sharp pain in the gum under the tooth whenever I put a little pressure on my face, like when I am washing it.

I have an appointment this week to have him look at it, but I am leary about going back to that dentist.

Any ideas what may be causing the pain at this point? I never experienced any pain or discomfort with the broken tooth before the crown was installed.