Barrel distortion is different from perspective distortion, which is easily correctible in Photoshop.
Barrel distortion is correctable, and there are two programs I know of that do it well. The easiest is LensDoc, which is a plugin for Photoshop. I seldom use it, but when I need it I am happy to have it on the hard drive. It is published by Andromeda.
The other is part of Panorama Tools, which has a correction tool that also is a Photoshop plug-in, but takes trial and error to get it right. You can download this free. I don't remember the URL, but do a search on "Panorama Tools" and you will find it.