I have often seen my beardies do that too, it is almost like they have a crop to store food in like birds do. I have seen one of my females munch a whole bunch of silkies and keep them there in her pouch, and then swallow them later.
If you are really concerned, use something plastic and fairly soft to open the mouth, I start at the corner of the mouth, once the mouth is open you need to put something like a pen or pencile all the way across to keep it open. The dragon will hate this, and fight a good deal so if you are by yourself dont attempt it until you've had some more experience.
If your dragon is acting normal otherwise, I wouldn't even try it at all, too stressful!
Sarah
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