If you have backups enabled via your iPhone/Apple Account you can try to restore your whole phone to a state before you first deleted the app. But I am not 100% certain this works.
If not, there is no way to restore them.
As seen here Nuki themselfes say “just add a new user to the smartlock”
https://nuki.io/en/support/smart-lock/sl-features/new-smartphone/
Unfortunatelly there is still no Backup/Restore functionality present or any sort of sync to an account where you can easily restore your previously configured nuki products. Nuki says “its for security reasons” but I call bullshit.
I had this problem once too and created this feature request but it seems no one cares about that.
See here
My “solution” was to add a new user to each nuki product which took quite some time…