If you look at the black box warning on the insert in the box of your Humira, you will notice that it says
some patients taking it experience more frequent upper respiratory and sinus infections. This is true of all the anti-TNF inhibitors. Some patients experience so many sinus infections they are forced to go off their anti-TNF.
Then again, it could be that you have been exposed to more bacteria than normal. I have read that this is a particularly bad year for upper repiratory problems.
Sure hope you aren't starting a flare! I find it helpful to eat yougurt whenever I take an antibiotic. It replaces the good bacteria that the antibiotics tend to wipe out.