This is normal due to the fibrosis/scarring that occurs under the skin. If you are satisfied with the cosmetic result, there is no need for concern. .
Thanks for your question. Believe it or not, this is a good thing. One of the things that we've learned about rhinoplasty over the last 30 years is that the skin contracts down against the nasal skeleton with a LOT of force following rhinoplasty surgery. It is important to reinforce the strength of the nasal tip cartilages to prevent collapse and a droopy tip. I always warn my patients that their nasal tip will be more firm than it was before, but it's doing important work for you. If you're worried, please go visit with your surgeon, but it sounds like this is nothing to be concerned about.
Based on the information you have shared, you only went to 2 follow up appointments after surgery. It takes months to heal from this surgery. You should have visited your surgeon on a routine basis. Without seeing a copy of your operative report online consultants do not know what was done in your procedure, so therefore will be unable to offer advice. I would recommend you contact your surgeon and discuss your concerns. What you have described at 4 years is unusual, and should be addressed.