OMG !! This is exactly what started my HA !!
I get VERY bad seasonal allergies in the fall. Last year where I live the ragweed and mold spores were incredibly high and my allergies were uncontrollable from August on.
Normally, after the first or second hard freeze of the fall the allergies decrease significantly and I start to feel better, however this year just as it started to get cold I got a SEVERE sinus infection.
So in mid November I had to go to the Doctor and get antibiotics. 10 days later I was better (for about 3 days) and then it went down hill again. Went back to the doctor. Now I also had thrush from the first antibiotics, so I was put on a second round AND on an anti fungal. This was the last week of December. I started to get bad nose bleeds out of my left nostril, and then started to smell cigarette smoke. The Smoke smell was INTENSE and everywhere I went. (even outside in the cold air it was like someone was holding a cigarette under my left nostril. Only thing that made it stop was putting tissue in that nostril to stop the flow of air.
That's when I went to our Lord and Savior, GOOGLE, and searched "Smelling Cigarette Smells that are not there" That's when I condemned myself to HA. I found a LARGE number of posts that talked about bad sinus infections and this symptom, but I found ONE post that said "Brain Tumor" and I FREAKED OUT.
In February, when my sinus infection came back for a 3rd time, I went to the ENT. He numbed my nose and looked way up there and said that everything was swollen, red and even weeping blood and that is was one of the worst sinus infections he has seen and put me on a 3rd antibiotic, this time for a month. After the month I was to get a CT scan to see what it looks like.
This gave me a month to get myself so worked up about a brain tumor (which the doctor dismissed off hand saying it was a sinus infection from hell).
I finally got the CT scan and the day after I took a CD ROM with the images to the ENT. That day I had such severe pain in the bridge of my nose it was crazy. I was SURE I needed surgery. I also start to get a numbness in my face (anxiety caused) that I have never experienced before.
Doctor looked at the CT and said, "Normal Clear Sinuses" Then numbed my nose again and looked up there. Slight deviated septum but nothing to worry about. Otherwise totally clear.
"But why the sinus pain, Doc?" I said to him. He shrugged and said, "Migraines perhaps. Stress Perhaps?"
I went back to my regular doctor and it was then that he diagnosed me with a severe anxiety disorder.
Gradually, since being on anti depressants the smoke smell has disappeared. I do sometimes think I am starting to smell cigarette smoke but it goes away quickly. The numbness in the face is still there most days, but even that is getting better with time. (crosses fingers that keeps improving)
My last follow up appointment with the Dr. I asked him (mostly for my own assurances) "So if I had a tumor that was causing symptoms like Phantom Smells, at this point, 6 or 7 months later I should be a very sick man, no?" He totally agreed and said that I DO NOT HAVE A BRAIN TUMOR, I have an Anxiety disorder and as I continue my treatment path, I am going to have bad days when I have physical symptoms, but hopefully if we are on the right path those days will become less and less.
I know this is a bit of a long ramble, but I hope it helps put your mind at ease that sinus infections AND STRESS / ANXIETY can cause these weird smells indeed.