I don't see the issue here OP other than having that copy could get you into trouble, but it is unlikely. Plenty of kids I knew had an instructors edition for one reason or another. Really there shouldn't be an issue since you should have access to it just usually through your professor. Then I doubt more than 10% of your grade comes from HW so you should be fine. However if you are that worried about it just return it or trade it in at your campus library. If you show them the receipt from your order I am sure they would understand.