The thing about respiratory issues is that they spread easily to other birds in the flock, including canker.
If that's not happening, then it has to be a blocked nare caused by dust, feed, debris from bedding etc...
Put one drop of water on the nare that you suspect is clogged, watch and see if it's exhaled out. You might have to do it a couple times to be sure the drop of water is being forced out or a bubble appears. If either occurs, then the nare is clear and okay.
Also, dont force anything up into the nare, like a toothpick, it can push debris further up causing possible injury.