ssh tunnel – Let user access my machine after lost users public ssh key

I have currently lost my servers data and needed to restore the server from the backup.

Unfortunately the backup was too old for a machine, that auto connects to my server.

So this machine cannot connect to my server, and I can’t connect via tunnel to the machine, because it can’t connect.

The machine is too far away, so that i can’t go there and get the public key again and can’t give it a new key.

Is there any possibility to let the machine get in again?

in the logs i see the attemptions of trying to connect, but unfortunately I don’t get the public key from the log.

So is there any chance to let the machine connect to my server?