Well, if you've had everything but the kitchen sink shoved into your sinus cavity before, it'll certainly feel like it's no big deal. I found the swab butting into the back of my sinus cavity uncomfortable, for sure, but it wasn't even
remotely close to other painful experiences I've had over the years. It may come down to the technique of the person handling the swab. If anyone avoids getting tested because of the discomfort, I'd say that would be silly and irresponsible.
Many years ago, I had surgery for a deviated septum. A couple of days after, the surgeon came into my room:
Surgeon: "Time to remove the splints from your nostrils."
Me: "Is this going to hurt?"
Surgeon: "What do
you think?"
Me: "Well...
now I think it's going to hurt".
Surgeon: *Has me lay on my side, puts a drip try under my nose, grabs one of the splints with his forceps and yanks.*
Me:
"HOLY $HIT!!!"
It was pretty intense, but subsided within a few seconds, thankfully. So, yeah, the swab is nothing compared to that.