Line on screen after LCD replacement

There are two possibilities here; either the replacement screen is defective or you may have incorrectly assembled the screen.

If you still have access to the original screen, you could try installing that one to see if the problem persists. If it does, there may be some damage to the logic board (probably the connectors). If it doesn’t, the go through this guide to double-check your work as some screens, especially lower cost aftermarket screens can be thicker and cause issues with pressure points.

Also, was the replacement screen a “complete” screen with small parts or did you have to transfer everything over? Pre-populated parts can be problematic but transferring parts can lead to alignment issues. Do some more testing and verification and come back with more details.

Final question, is the picture of the phone innards your device or a photo from the web? It has an awful lot of scratches, markings and the battery looks like it has seen better days. Let us know if the phone has been previously repaired.