You must first get your nose examined by ENT specialist
that you really have deviated septum which can block or its something else.
Get your thyroid
status checked get done (T3 ,T4 ,TSH blood tests).
there are many other conditions whichcan cause nasal blockage not just deviated septum.
So dont get upset you might not require surgery at all.
Go see a doctor .
And start doing moderate exercises or atleast brisk walking that will secreat adrenaline
in your body which will open your nose as it is a natural decongestant. and will help in weight management