Dropped m9 in toilet. Dried and working, but screen flickering

[problematicsloth]

So I stupidly dropped my phone HTC m9 in the toilet. Didn't realize it was in my back pocket. Anyway, was still working when I pulled it out the toilet. Immediately powered off and dried as much as I could. Left for approx 24 hrs in a bag with a nappy (lol) and rice. Turned on. Works...but! Screen slightly flickers!
Is this because it was not 100% dry when I turned it back on? Or is this just irreversible water damage? Is it solely the screen or will this phone just eff out at some point n the near future? Oh I also put the phone on charge once I turned it on...was that a mistake?
Edit: I should add the phone works fine. But every now and then the.. brightness... Of the screen looks to be slightly dimming and then returning back to normal, and keeps flickering like that for a while. Then stops. The. Does it again. Doesn't affect the usability of the phone either..

 

[Carlo Villa]

Do you have insurance? Can you replace it?

 

[problematicsloth]

No insurance. This was a phone sent out by our phone company with the renewal of a plan.
Did you think it's a problem that will just get worse,?

 

[belodion]

Water damage is progressive, alas.