3 months ago I noticed a small opening there. It got bigger as time went on. I've rarely seen him rub it against the cage wire to get itchy. I think if it was because of friction it would have been on the other side.Oooo that's interesting
Isn't scaley mite that much I do know
I would be thinking like DianaT that your bird is rubbing on that side
Skin doesn't look sore but the nare (nostril) on that side looks different somehow not sure if it's just the photo of if it really does have a colour tinge in one part of it. I would be popping to an avian vet (not a general or exotics vet) to get it checked out. Suppose there could be internal irritation going on or a sinus issue that could be flushed but would have to be diagnosed and done by an avian vet.