Bottom left of screen turned grey/black after the screen replacement

I bought a cheaper iphone8 plus with shattered screen . I was hoping to fix the screen and start using it. I replaced the broken screen with the new one. When I turned on the phone, the bottom left of the screen turned greyish/black. I thought that it must have been the circuit problem. I uninstalled the screen and reinstalled it but it still the same. Old screen didn’t have that issue. What could be the problem. Please help. Thanks