Did you leave your snake alone without any handling or anything for a few days? If not, it may be too stressed out and doesn't want to eat. How big is your snake? It's possible that the petstore sold you a baby that hasn't fed very much and may not be a confirmed eater yet. Go on the search section and type in feeding suggestions. There are a lot of references. You can try cutting a slit in the pinkies head, and smearing a little brain matter on it to help entice your snake. I would also place it in a small container that it can hide in with just the pinky. Perhaps the container it came home in can be placed in the viv with the snake and the pinky in it. Make sure you don't feed on any substrate so that the snake doesn't ingest it. Sometimes you can try a paper bag. Put the snake and a pinky inside and close the bag. Put it back in the viv overnight and then open in the morning. A lot of shy eaters will eat in that. Scenting pinkies with anoles works on some as well. I would suggest you get The Cornsnake Manual by Kathy Love as soon as you can. It's a great resource for answers of all kinds.