Unfortunalty, this is a problem in the lock cylinder and the entire lock is replaced, which comes with a new key set. Be sure your shifter is going completely to the park position...try putting it in gear again and than back to park and see if the key will release. The problem is that if it is the lock and you do get the key out, it may not go in and turn the next time; but you can try to spray some WD-40 in there to help work the tumblers loose.
Yes, that is my recommendation, becuase once the tumbles release they may not allow the ignition to turn again...than you'll need to tow it to a repair facility...but if you would like to try it you can spray the Wd-40 in there and the key may very well come out and even work for some time. Also, some mobile locksmiths can repair this type of tumbler and they come to you.