Yellowish Box on the Screen Display after Water Damage

Hi After a couple of months (since May 25th) of trying to repair my MacBook Pro 2018 15’inch due to water damage, a repair man was able to turn it on but it has this Yellow Box on the screen. Is it possible for the Water to have the screen having that Yellow Box on the screen? The water only had contact with the inside cause it enter only through the bottom panel vent hole of the MacBook. Now I have this Yellow stain on the screen.

Please is there anything that can be done or I hope would solve the Yellow box on the screen issue? Water never got to the screen how could it be and if it the water destroyed the board components working with the screen display can’t it be cleaned or something so it doesn’t affect the display.

Thanks.