accidentally deleted my photo library on mac air m1

If it’s in the Trash, go there and Restore it. If you’ve emptied the trash, and you’re not using iCloud Photos, it’s gone for good unless you have a backup.

Every Mac has Time Machine, Apple’s excellent and free backup software. External storage is cheap (most people don’t need a fast SSD for a backup, you can get a good 2 TB HDD for $65). If you don’t regularly back up your data, perhaps this will be the impetus to start. Some lessons are hard, unfortunately.

If you deleted your photos – but not the Photo library itself – check the Recently Deleted album.

When you delete a photo or video from within Photos, it moves to the Recently Deleted album, giving you a 30 day window to change your mind, and restore it. If you let 30 days pass, or you delete a photo or video from within the Recently Deleted album itself, it becomes permanently deleted.

Then you can't get it back (unless you have backups or copies somewhere else, outside the system).

Restore it from your backup.