Nice rifle! It depends on the shape and depth of the dent, but I think you might be able to push it out from the inside. If it's not too deep or cracked, you can try this method:
1. measure the inside diameter of the rod sleeve (called a tubular magazine). Sorry, I don't have one, so I can't tell you exactly what this measurement is.
2. Go to you local hardware store and buy a hardwood dowel rod that is just slightly smaller in diameter than the tube.
3. Round over the end of the dowel slightly with some sandpaper, clean and wipe it down with gun oil.
4. Slide the dowel into the tube until it reaches the dent, and tap it until it begins to pass that point. Don't let it go too far past, or it will be difficult to pull back out. Don't force the dowel into the tube if it doesn't slide freely (up to the point of the dent) or you won't be able to remove it. And don't push it past the point where you can grip it securely.
5. Pull the dowel back out, rotate slightly, and repeat.

But, use your best judgement: If it doesn't look like this method will work based on the shape and depth of the dent, you should take it to a competent gunsmith, and let them sort it out. Assuming that the rest of the rifle is in good condition, you have a classic that's worth repairing. Best of luck!