I think, first of all you have to pass the exam. Your exam ended before Dec’13 does not implies you have passed the exam. If you pass the exam you will get the increment from Jan ’14 which you will get as arrear.
A little amendment…. You will get increment from the very next day on which your exam was over (not from the next month), but all you have to do is to pass the exam as has been told by saij. Thanks.