It's difficult to know what it could be. Continue to follow the advice of your surgeon as he/she has examined the area and does not seem to be concerned. Be sure to keep your follow up appointments and notify the surgeon if any changes occur during your recovery.
Thank you for your question.I would follow the advice of your surgeon, without a photograph it is hard to give you my opinion but It is most likely a suture that has migrated. It is important for you to schedule an appointment with your surgeon for a physical examination and fix the suture to prevent any other types of complications or infection from occuring. I hope this helps.
Best of luck in your recovery!
James Fernau, MD, FACS
Board Certified ENT
Board Certified Plastic Surgery
Member of ASPS, ASAPS, ISAPS, The Rhinoplasty Society, AAFPRS, OTO/HNS, ASLMS, International Federation for Adipose Therapeutics & Science