If this fish is the only one that you have caught that looks emaciated then I would not worry about it as it could be a result of an injury from being hooked previously. If you are catching a lot of small/stunted/emaciated bass then you need to introduce more forage and remove stunted fish ASAP!
Adding some bluegill or golden shiners will help dramatically but they won't spawn in the winter so it would make more sense to stock them in the spring. In the meantime cull out any and all undersized bass you catch.