I did an erase on my internal now it won’t let me reinstall iOS

Welcome to Apple Support Communities.

Please follow these steps:

1. Shut down the Mac.
2. Turn on the Mac, and immediately press and hold Option + Command + R until you see a spinning globe.
3. Once you are in macOS Recovery, verify you are connected to WiFi in the top right corner. If possible, connect directly to the internet with Ethernet. 
4. Go to Disk Utility.
5. Select "View" in the toolbar > "Show All Devices".
6. Select your main hard drive or SSD. This will be the top, non indented hard drive. 
7. Click Erase, and input the following exactly: (If you cannot select erase on the main hard drive, erase the "Container" or “Macintosh HD”.)
8. Name: Macintosh HD
9. Format: APFS
10. Scheme: GUID Partition Map (if shown)
11. Click Erase. If “Erase Volume Group” is shown, use that instead. 
12. Quit Disk Utility
13. Go to the reinstall macOS app.
14. Follow the prompts, and install on Macintosh HD.

Jack

You need to make sure you erase the Volume Group for Macintosh HD. Boot into Recovery OS then open Disk Utility and change the View to "Show All Devices". Click on the Container that holds Macintosh HD and Erase that Container. This will remove all volumes and format a new Macintosh HD volume. Last, try your reinstall again.

I have accidentally Deleted iOS from Mac now can’t reinstall iOS in MacBook