To me that looks like a stomach prolapse, which is what frogs do when they cannot regurgitate something they've eaten. However, the stomach is usually re-ingested within a few minutes, so this is bad.

It may be something else, but I'm not sure. However, someone much more experienced than I will comment within the next few hours, possibly even within the next few minutes.

A trip to the Exotic Vet may be needed to save your frog. For now, place him into a spare tank with moist paper towel for substrate, a dish of dechlorinated water up to his neck, some cover, and preferably a wallpaper. More photo's of the frog, specifically it's face, could definitely help us out, as well as a photo of the tank. I would keep the "stomach/tongue" moist by spraying it with dechlorinated water for now.

Also, what have you fed him over the last 48-72 hours? If he's eaten a pebble/stone or something he could not regurgitate that may have brought it on.