Google Nexus 5 :: Screen Goes Black?

So here is the deal: I have a nexus 5 that fell into water 1 month ago, i did all the procedures, rice + brushed all the circuits with isopropilic alcohol (100%) (oh, it stayed like 2 hours under water!). After doing that amazingly the cell phone was working perfectly, until after one month the screen started going black:

1- turn the cellphone on

2 - everything works fine, i get to the unlock phone screen

3 - while at the unlock phone screen i can see notifications for exemple, turn the cell phone to airplane mode, etc.

4- once i click on a notification or i unlock the screen, the screen goes black. and it happens every time that i unlock the screen

Sometimes i turn the cellphone on and it works normally for a couple of seconds or a couple of minutes and then the problem comes back. First i tought it could be a software problem, so i cleaned the cache, it didn't work. Then i did a factory reset, the problem was still there, so the only guess left for me is that something is malfunctioning because of the water damage. But, it only turns black once i unlock the phone.