How do I fix this problem on my ipod touch?

So i tried to download an app on my ipod and it said unable to purchase but technically i purchased it and it had the shortcut of the app on the app screen. but it was not downloading and now it just sits there and it will either download in a couple of days or delete itself and i try it again. is there anyway i can delete it or something because it wont let me do that with the original way to delete apps. How do i fix it.. please help