How to resolve flickering issue in my phone

Dinesh Rawat since it did have some water exposure (no matter how slight it might have been) you do need to try and resolve that. For now you want to stop continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse as this may further damage your phone.

The next thing to do is to clean it. Disassemble your phone using something like this video You must remove all EMI shields from your circuit board. If you do not remove those, you might as well not do anything. After you removed those, clean the whole board, connectors and all with +90% isopropyl alcohol. Follow this guide, and even so it was written for an Apple iPhone 3G, all the points are still pertinent to your phone. While you clean your board, check for any obvious damage, like burned or missing components etc. When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Best thing to do would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Once all this is done, Replace the battery and reassemble your phone and reevaluate. It is possible that you only have a damaged display but it is also possible that you are having shortened components on the board. Until it is cleaned, everything will only be a guess. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try.