The answer to your question depends on you to a certain degree.
While septoplasty or rhinoplasty will typically affect your nasal resonance, the change is often imperceptable to others. If a change were to occur, most singers feel that it is a positive one. Having more air flow through the nose tends to open up the resonance, reduce effort, and can help with upper register as well.
HOWEVER, if you are known for having a voice with a more closed nasal resonance, then the surgery may cause problems. The only way to recreate your previous sound would be to use your palate differently and close up the nasopharynx again. This usually takes some time and lots of work with your coach and may never fully recreate your preoperative sound.
So it depends on you. Hope this helps
Best of Luck