I think I might have a tooth abscess, but my rhinoplasty is scheduled in 3 weeks. What should I do?

It is not absolutely necessary to reschedule your rhinoplasty. Yes, you should take of your tooth immediately. If your infection clears within a week or so and you take enough antibiotics preoperatively to clear the infection you can proceed with the surgery. If the infection is not under control according to your dentist and your plastic surgeon you will need to reschedule the surgery. 

Thank you for you question.  Your concern is not misplaced.  It is important that you have your dental issue resolved prior to elective surgery.  Having an active dental infection places you at undue increased risk of post-operative complications.  Make sure you see someone for this as soon as possible and if needed, reschedule your surgery.  Get better! 

It would be critical that you fully solve your tooth abscess before undergoing rhinoplasty. If this involves and extraction and you get it done now then your rhinoplasty date will not be affected. But if involves root canal and other therapies that are more prolonged, you will need to push back the date of your rhinoplasty surgery.