Go to a good fitter and he'll see how bad it is. You can add extra insoles, or get proper footbeds and put those on top of your stock insoles. It's better to add rigid material under the liner though. You can pad out a boot to an extent to reduce the volume but a good fitter will be able to tell you if your boots are way too big or wide for you and would then suggest a new pair. If you're stuck for cash it's worth a shot seeing what you can do with what you've got though. Mods might cost you about $60, and good footbeds $100-200, but those can be transfered into new boots and a good pair will last you a lifetime.