Water Damage ...and Dead Power Supply Unit

@rudranshutiwari you have not told us if you took care of the water damage. I would suggest that you clean it of the water damage. For that you will have to disassemble your phone Since iFixit does not yet have a specific guide for this, use something like this video Remove the main board and the charging board. You will have to remove all the EMI shields off those boards. If you do not remove the shields, you are not cleaning the board.

Take a close look at all components and connectors to assess the damage. Look for major corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. Once you got any gross contamination cleaned, use 90%+ isopropyl alcohol and clean your parts some more. For a proper cleaning, use this guide. It was written for an Apple iPhone 3G but all the steps are still pertinent to your phone as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning. While you clean your boards, check for any obvious damage, like burned or missing components etc. The importance here is the cleaning. All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner.

When it is properly cleaned, replace the battery. This is a must and not an option. It will fail if you do not take care of it now. Now is also the time where you will need to change the Sub board (small board on the bottom which is your charging board, shown in the video at about 1:00min)

Now reassemble your phone and re-evaluate.