Is the bump on my nose scar tissue?

It would be helpful to know how long ago you had your last surgery. If your surgery was recent, you likely still have swelling throughout the nose that is present. As the nose heals the swelling will continue to go down. Hard to say if there is an element of scar tissue present in that area of your nose. I would recommend following up with your rhinoplasty surgeon to get a thorough evaluation of this area to determine what is the likely cause. If you feel your concern is not being addressed, it is always in your best interest to get a second consultation.