External light keeps switching on and off (extreme heat)

First off, hello everyone. I hope you’ll be able to help out.

My device’s light (the one on the back for photography and the flashlight) keeps randomly turning off and on, overheating and draining the battery in the process.

What I have observed: Sometimes it is off for hours, sometimes it flickers for hours, at other times it’s simply on and won’t switch off. I can’t use flash anymore while making photos. The flashlight works and only lessens the strength of the light!

By switching the phone off, the light turns off as well. Once I charge the phone, the light immediately starts flickering and flashing up again.

Important note: The problem started happening after the phone got wet. It stopped working entirely, so I opened it up, took out the battery, and cleaned it with an air-pressure pump. As far as I could see, no water touched the electronics, except for maybe some metal parts of the battery (it was hard to see), as well as a build up of moisture behind the camera lenses. After cleaning the phone (it’s 100% dry now) I charged it and it started working again.

Is this some sort of safety-mechanism in order to drain the battery and protect the electronics? Is there something I can try to identify the problem with more precision? Might it be a bad electrical light circuit?

I’m dirt poor so letting it repair probably won’t be an option for me. Maybe I might be able to buy a new battery but would that really help? Is there anything I could do?

I was even thinking about (in the worst case scenario) destroying the light itself in order to save the battery. It might stop the overheating and might not have any negative effect on the phone overall.

Please help me out here before I do something stupid. Thanks a lot!