A sinus infection is not easily contagious in most cases, but can result from a virus, bacteria or allergies. So the infection itself is not contagious, most of the time (as they are usually secondary infections), but the virus that caused it can be contagious...That having been said, viruses are not the only cause (you can basically give one to yourself if you have inflammation).
If you get some inflammation up there and things don't drain like they should, that can cause a sinus infection (even if it started from something innocent like allergies) because things get trapped and then fester.
They can carry bacteria, but so can a human hand etc (my bird has licked my eye/nose by mistake before and it's honestly a bigger hazard for them than you in most cases)-- You could have just caught a cold that turned into a sinus infection...
Your doc sounds very strange-- I get sinus infections every year and they are always are always the result of a virus...So I get sick with a virus and then because of that, things get congested and then I get a secondary sinus infection. Unless you are severely immuno-compromised (as in going through chemo) the odds of a bird that has been tested for the scary diseases passing something to you is low. Did he swab you and find some strange "avian" bacteria or virus? BECAUSE, the harmful bacteria that they can carry is also all over the place in our environments (excluding the bacteria that causes psittacosis, but you said your bird was tested and I am sure they ran that test-- it's standard)...In terms of general viruses/bacteria, you touch something, then rub your eye or nose and bam..touch your phone that hadn't been disinfected and then eat food, touch your lips, itch your nose, rub your eyes...BAM...you breath in a public space...BAM.
There is NO way he could rule out all of the common things that cause sinus infections UNLESS he found the specific bacteria that causes psittacosis, and in that case, he is still ridiculous if he wants to call psittacosis a "sinus infection"...probably isn't a fan of birds lol...Did you get tested for psittacosis? It's a reportable disease, so if he suspects you have it, he needs to report it to a national database (in the US anyway)...
Saying your sinus infection came from the bird is ridiculous, but saying you caught psittacosis from the bird is possible (it's semi-rare, but it does happen and not everyone gets sick with it to the same degree). That having been said, your bird was very likely tested for this already.
Here are the steps for diagnosing pssitacosis (from healthline.com)
https://www.healthline.com/health/psittacosis#diagnosis:
"To diagnose parrot fever, your doctor will generally perform several tests. Blood and sputum cultures can reveal whether you have the type of bacteria that causes this infection. A chest X-ray can show the pneumonia that is sometimes caused by the disease.
Your doctor will order an antibody titer test to see if you have antibodies to the bacteria that causes parrot fever. Antibodies are proteins that the immune system produces when it detects a foreign, harmful substance (antigen) such as bacteria or a parasite. Changes in the level of antibodies can indicate that you have been infected with the bacteria that causes parrot fever."
