3 months post op. Why is the skin under my nose tight? Can a columella be widened/protruding if it was thinned/retracted?

It is difficult to provide an explanation without seeing your photos or examining your nose.  That being said, it is possible that there was elevation of the columella and/or tip, which might explain your situation.  These maneuvers can lead to benefit, but if done excessively, may lead to an undesired outcome.  I would approach your surgeon with your concerns.

Dear Realself user,It sounds to me that you should go and see your own surgeon who operated you so you can ask him all these questions, he or she will know best what had been done to you and could help you further.
Best of luck,

TAS Aesthetic Surgery Clinic