Hi Sasikanth,
The situation looks tricky. Let's go step by step.
Step 1 - An error has occurred till 31.12.2015. The condition is posted.
Solution : End this condition by putting the valid to in the condition.
Step 2 - Create new condition type and assign correct flow types to it and start the validity of this condition from 01.01.2016.
Step 3 - Error must have resulted in wrong posting affecting your financials.
Correction step - Either use one time posting in REFX or pass an adjustment entry directly in FI with reference to the contract.
Assumption - The posting period is closed and can not be open.
REgards,
Amar