Lost .ppk file - Cant access my files

The .ppk file is the private key, this cannot be recreated or regenerated if it is lost.

Depending on the version of Linux that is being used, some (or all, or none) of these actions here may be of help https://repost.aws/knowledge-center/user-data-replace-key-pair-ec2

Othwerwise, create an AMI from the running instance and then provision a new instance with a new key https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/creating-an-ami-ebs.html#how-to-create-ebs-ami