That is a pretty severe prolapse. If it is only a prolapse I suggest sprinkling sugar or trying a honey bath to make the swelling go down and maybe make it go back in, though that won't help if a cut is to blame. It's probably of pretty questionable help since the prolapse didn't pop out on its own.

Whatever the case, I wouldn't try to feed the frog just now.

You could try a vet, if you want. I am not an expert but this looks most likely fatal.