Nasal Voice 3 Weeks After Sinus Surgery. Will It Go Away?

The symptoms you are describing, particularly the
changes in the sound of your voice, are not uncommon and should not be the
cause of major worry. Your body is still responding to the stress of surgery. In
fact, three weeks is still relatively early in the recovery period, so I would
suggest trying to be as patient as possible as you continue to heal. If the
problem persists, schedule a follow-up appointment with your surgeon to
evaluate your recovery and your condition.

In the first few weeks after nose and sinus surgery, a lot is going on. This includes excess mucus production, and significant swelling.

All of this in turn will have an effect on the resonance of the nose, pharynx, and throat (how it all vibrates). Until all the tissue has no more swelling, you will continue to have subtle changes in the voice quality.

The fact that you did have the surgery will result in some slight change in the overall resonance, but not likely anywhere near as much as you are noticing currently.