Is connecting a screen to a (dried off) waterdamaged phone a bad idea?

I just finished rebuilding my iPhone with a new battery, charging port flex cable and housing.

The first two attempts at turning it on with a screen connected resulted in gray bars at the bottom of the display that continued getting stronger/brighter until it shut off. The third time the screen remained off but the phone seems to have booted, pressing the power button seems to turn on the backlight (can see edges glowing on bottom of display) but from the front the display appears to be off and does not display anything.

My primary question is: will I have to buy another display? Will connecting a screen to a water damaged, but dry, phone cause damage?