boot loop after boot camp partition deleted

Hello,

I have a 2020 Intel iMac 27” 256GB

Today I deleted windows 10 from my iMac, through bootcamp.. I believe I deleted the partition in my hard drive which then returned the storage to my main Macintosh hd hard drive. After restarting, my iMac has been stuck in a loop, it asks for the password for my encrypted Macintosh hd hard drive and when I put this in it goes black chimes the Apple classic sound and begins the reboot process again…. I have got several years worth of backups but when I go to restore from a backup it tells me to reinstall MacOS then use migration assistant.

Do I now have to erase my hard drive and reinstall macOS to get my data back.?

Any help is greatly appreciated, I have years of academic notes stored on my iMac.

Many Thanks

S