My 7 Year Old Corn Snake Just Laid An Egg, It Has Never Mated With Another Snake. What Do I Do With The Egg And Could It Be Fertile?

Actually, by far, most reptiles do reproduce sexually, but an asexual form of reproduction has been seen to occur naturally in certain species of whiptails, geckos, rock lizards and komodo dragons, and a few snakes (not corn snakes)... But it's very rare. The offspring produced by parthenogenesis are almost always female... And are in essence little clones of their mother.
 
Many birds and reptiles will lay eggs whether or not they are fertile... She'll more than likely lay more... When she's done you can simply remove the eggs and dispose of them however you see fit.