Assuming there is no fault with the parts used, you'll need to run Google's repair tool, it's pretty simple to use but does require a computer running windows.
https://pixelrepair.withgoogle.com/
The program should walk you through it step by step, but essentially, you'll need to download the software, launch your phone into fastboot, and connect it via a sync+charge cable to your computer (the one included with your phone should work, however some third party ones do not)
There's some debate over whether or not this requires a factory reset, and while I don't believe it does, always make sure to backup your phone before doing any kind of debugging.
Coco,