Well, you could be... depending on how much you've used. Most courseworks are filtered through using a software and it checks up against the web etc... If you're in year 11, don't worry anymore and hope for the best on results day ~ :] (Why didn't you think of it before?)
If you're in year 10 you could beg the teacher to let you re-do some parts so all's good. If you haven't handed it in yet, just tweak it a bit - most songs are horribly cliché anyways. Though I'm really liking the "42 grams of heart attack" :]