There should be no pain experienced during the actual deviated septum surgery.
The surgeon should put you under anesthesia so that you do not experience any pain and the surgery should go through just fine.
However when you wake up after the deviated septum surgery then you might experience some pain for a few days to a week after the deviated septum surgery.
But after awhile the pain after the deviated septum surgery should go away.
Your doctor can usually prescribe some pain medicine to help the pain go away while you're recovering from the deviated septum surgery.
You might also have a little bit of swelling after the deviated septum surgery but that should go away within a few days.