Depends. Have you changed tank conditions lately?
Are the scales standing up on the cory, making it look like a pine cone? That is usually the first sign of a fatal disease known as dropsy.
Sometimes female cories become bloated when they fill with eggs. This is one of the ways they can be told apart from the slender males. My three females look like whales compared to my one male.
Also, after they eat they tend to look a bit pudgy. Cories that live a life of copious food do also get obese the way humans can get obese, especially if they have lived in a small tank for most of their lives.
So it really all depends upon whether your fish is behaving normally or not. Your fish being fat might be normal for your fish.
~~Colesea