No, once a Checkin is no longer in pending status and has received approval or rejection to apply to a guest account it can't be edited.
If you'd like the ability to edit approved/rejected Checkins reach out to your CSM to submit Product Feedback on your behalf. The Product Feedback will inquire with our Development Team if the feature can be added to the development roadmap.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)