No, let's not have a post about whether or not to take off one's shoes. Please. I'm begging you. :-)

You can paste the wallpaper back down easily, there is even wallpaper paste available in a little bottle with a sponge top (like a shoe polish bottle) just for lifting seams and edges.

Now, what do you have for trim? If it's painted, you're in luck. You can get a wood trim piece called an "outside corner molding" (aka corner bead molding or L-corner molding) that wraps neatly around the corner at Home Depot, and it's quite cheap in its plainest form. Predrill the trim and install with thin nails, fill nail holes with a bit of wood putty and sand that smooth, then prime and paint to match the trim. Burton Moldings has a couple of fancier ones in MDF, too. If you have stained trim it'll be a little trickier but with some hunting around the Web and even a local full-service lumberyard (not a big box store like Home Depot) you'll probably be able to match the wood species so you can try to match the stain color. If you have very fancy trim, like Victorian style, there are fancy turned corner beads as an option as well. No more worry about peeling wallpaper on that corner.

johnmari beat me to the answer. The other thing you can do, if the molding can't be done for some reason, is to put a large potted plant, like a tree, right at that corner, so that people can't grab it. Or rearrange the furniture so that grabbing that corner is just not a good option. Or put a picture or a mirror right where people are putting their hands--they are far less likely to touch a mirror than the wall.