Why my phone is overheating even on standby mode?

I'm facing an overheating issue when water accidentally entered into my charging port. My device gets heated even on standby mode. Overheating was an issue with my device before this accident happen but that was when I used to game or surf the internet. Now it keeps heating. Heating starts from the upper end of the screen from where the earpiece is. The area gets very hot and the remaining phone. Please help why is it happening? Does factory resetting will fix the issue? or i've to replace the battery as the battery also gets hot. When water entered on my phone, it gave a warning that I should download a battery application for my phone. I didn't understand.. Please help