How do I fix this?
OS: elementary OS 5.0 Juno x86_64
CPU: Intel i7-7700 (8) @ 4.200GHz
Memory: 3219MiB / 16005MiB
GPU: NVIDIA GeForce GTX 1070
GPU Driver: NVIDIA 418.56
Press Ctrl+Alt+F2 to get to a command prompt. Login there and press Ctrl+Alt+F7. It should load your desktop.
Once that's done revert everything you did while installing that nvidia driver and install the driver avaliable from Appcenter on the Installed tab.
The driver you've installed is an unstable version that's not supported by elementary so it's normal to find errors.
If you don't know how to remove the first driver you better backup your data and install elementary again. Then just install the driver inside Appcenter.
sudo ubuntu-drivers autoinstall