I have been reading up on this all morning
did you read and follow the instructions for installing POP ????
if pop opens and runs ok , you may not have completed the install procedure
Updating GRUB
You may have noticed your system booted directly into the Linux partition without the Windows 10 option. Now we will update our system and help GRUB recognize the Windows partition.
1. Update Your System
Boot into Pop os
Open a terminal and run the following commands:
sudo apt update
sudo apt upgrade
2. Installing OS-Prober
Now we will install a tool to help Pop!_OS recognize the Windows partition.
Run the following commands:
sudo apt install os-prober
sudo os-prober
You should see something similar to /dev/sda#:Windows 10:Windows;chain
Run this command so GRUB can update with the new partition data:
sudo update-grub
Dual Boot Complete!
Now when you restart your computer you will be greeted with the GRUB boot loader on start-up. You will be able to select the partition to boot into. By default it will be set to Pop!_OS so you will have a few seconds to select Windows before it automatically boots into Pop!_OS.