Scar stinging. Is this the start of an infection?

Without an assessment in person it is impossible to comment. Please address your concerns with your surgeon. Regards, 

Hello,
Thank you for your question.
It is difficult to say without an assessment.
I'd recommend voicing your concerns to your Board Certified Plastic
Surgeon.
All the best.

Thank you for your question.  3 weeks after surgery is a bit late for a typical infection.  Without pictures it is difficult to tell for sure, but I think there's likely a combination of a couple things going on.  Your scar being raised and red is part of the normal healing process at around 3 weeks.  This will continue for a couple weeks and then slowly soften and decrease in color.And at the ends of your scar, it is possible that some of the dissolvable sutures that were placed under your skin are starting to work their way out.  This isn't a problem but it can definitely cause some discomfort.  Give your surgeon a call and see what he/she thinks- there are a few tricks that can be used to minimize both of these issues.Good luck,Dr. Seth