Go to the dentist. Find a clinic. Or a lot of dentists have low interest financing companies now. I had a similar situation with a cavity close to the gum line and was putting off going to the dentist. I was sure it was going to be a root canal or extraction but they were able to fill it.

It's only going to get worse the longer you put it off and it might not be as bad as you think. If there's any chance that it's not a root canal yet you should get it taken care of. It'll be a lot cheaper and/or better than the alternatives.