You can actually consider both. Once you've deleted a transaction in QuickBooks, there's no record of it anymore. So, you can either shred your physical check or stamp it as "Void" if you aren't going to use it anymore.
But if you want to still use the check, you can recreate the check you've deleted. Just go to your Audit Log so you can review the details of the deleted transaction.
Please let me know if you have any other questions.