LCD monitors are highly sensitive—and not cheap—so you should avoid running with scissors near your screen whenever possible. If you do somehow damage the liquid crystal display, follow this advice from PC Extreme:

For a temporary fix:

• Clean the surface of the screen with diluted isopropyl alcohol (50/50 with water) with a cloth—not toilet paper or paper towels. These will scratch your screen.
• Fill the crack with Vaseline.
• Gently wipe off the Vaseline outside of the scratch.
• When you are done there should be enough Vaseline to fill the scratch.