Battlefield 3 Limited Edition Code

Hi I recently purchased a used copy of battlefield 3 limited edition and I saw that it came with a redeem code for the expansion pack "back to kurkland" but when I went to type the redeem code in, it had already been used.

So my question is do I need to buy a new copy of the game in order to use to redeem code or is there some other way that I can get the code.