How to Tighten Nasal Skin After Rhinoplasty?

 It takes 1-2 years for this to happen and there is nothing to do to make it go faster. If you skin is thin, I would avoid cortisone.

Typically the skin tightens itself after a rhinoplasty. You did not mention how long ago you had your rhinoplasty. Give it at least a year before you address the skin issue.
Also, please remember rhinoplasty is done for making the looks of the nose better, not its feel. If your nose looks better, then do not let the feel of the skin bother you. No one is going to touch your nose and feel it.
Regards

It is usually not necessary to remove skin from the nose during or after rhinoplasty. The skin generally shrinks to fit the new contour over the year following the procedure. I wonder if you really need skin removed or if you are just not pleased with your new shape -- for example, is the tip droopy. Nonetheless, I have performed procedures to tighten the nasal skin in some patients; there are numerous laser based skin tightening procedures that may help you in this matter.

I have never seen skin not tighten enough after Rhinoplasty if given the appropriate year or two.  It is possible that you have very thick skin and this might result in a longer post-op course.  In the area above the tip it may help to inject steroids as well.

The nasal skin will naturally tighten over time. It will take a year or longer, depending on how much cartilage & bone was reshaped. Thicker skin will take longer than thinner skin to tighten. Sometime a small dose of steroid injected directly onto the top of the nose may help swelling & skin tightening. Gentle massage may help a bit too.
Speak to your rhinoplasty surgeon to see what can be done to help the healing process.