What Causes Persistent Blockage In Nose During Mornings?

I can smell smoke..maybe its the airconditioning. I havent smoked when I did it was...casually for 5yrs. I had two bouts of sinus infections winter just gone with nasal spray and antibiotics...the smell has been about for 2-4wks now. I have a blocked nose each morning. I thought it was the heat.. What could it be?