Any surgery has the potential to be a “big deal,” primarily because of the anesthesia and also because of other types of unforeseen risks (i.e. blood clots and conversely,uncontrolled bleeding, infection, sudden drop in blood pressure).
That being said, rhinoplasty is one of the most commonly done surgical procedures today, and in the hands of a skilled surgeon, can be very beneficial, particularly if you have breathing issues as well as self-image concerns. I have never had this type of procedure, but I know people who have, and the medical field has come a long way since the earlier nose jobs. They are able to minimize the down time, and help with pain management. But make no mistake this is not something to be done lightly without doing a LOT of research about it. I leave the issues of halacha to others to discuss.