I whimpered and called the dentist in the vain hope that they'd still be open half an hour after the time I thought they were supposed to close. They were. *glee* I have an appointment on Monday. Meanwhile, I will be managing the situation with a combination of topical anaesthetics and internal painkillers of types suited to the task at hand.
But at least I know what it is, and I won't be blaming dry socket or anything crazy like that. I have a sinking feeling it's going to be another root canal.