Green card mutilated

My green card is mutilated, I applied for citizenship July 3rd 2012, took fingerprints September 14th 2012, had the interview October 29th 2012, interview was rescheduled due to sandy hurricane, had new interview December 6th 2012 passed the test but I'm pending due to background check hasn't come back yet, I have to travel abroad before the 25th but last time i came in thru customs they gave me a hard time because my card is mutilated and they didn't care about the letter of my citizenship appointment, they wrote something in the computer and the officer told me "next time you come thru customs you better have a new card or a blue passport" what are my options to come back without having a problem?, i have no idea how long the background check would come back, the officer who interviewed me just told me "if the background check comes back clean you would received a letter in the mail to due the oath" he didn't specify when, just said "maybe" before the end of the year but i doubt it