my ent doc is dr koay cheng eng too.. i am still recovering from the surgery he did on me last week.
what i had was deviated septum/chronic rhinitis and allergic rhinitis..
i have been using a lot of nasal decongestant spray since the last 2 years and finally decide enough is enough and i really need to do the surgery..

airflow is good right now(previously my left nostril was blocked 95%) and i cant feel the stitches. the surgery fixed only 1 part of my problem.
the other part of my problem is allergic rhinitis, any external elements like dust, pollen, oil vapour and smoke could trigger my inner nose to swollen up..
right now i am on prednisolone, a steroid based anti histamine to stop my nose from getting swollen but i'm pretty sure it will return once the prednisolone stops..

i believe what you are experiencing is the same as me, you might have allergic rhinitis too.. using anti histamines are really only short term solutions as they inhibit the inner nose from getting swollen, not resolve the issue why it gets swollen in the first place.. i have been reading some local papers promoting a vegetable based supplement that could help sufferers of allergic rhinitis, the supplement is called nuvalectranal.. i will be trying out this supplement soon after my next check up with dr koay.. i would suggest you check with your ent doctor too whether nuvalectranal or some other allergic rhinitis medication is needed for your blocked nose.. the key thing is to ensure the medication fixes the root cause of the swelling, not just blocking the symptoms/swelling..

attached are the paper article i read last week regarding allergic rhinitis..