Your frog may just have to take a giant dump... I had a similar panic situation with one of my frogs a long time back. His one side was bulging WAY out to the point I thought the poor guy was about to explode. After one enormous poop later, the bulging side was back to normal and he was good to go.

Of course, if this persists for an extended period of time (e.g. more than a few days), you may want to look into this further. Just thought I'd share my experience with a similar situation in order to avoid any unnecessary or premature panic.