Max. time for a change to your Authoritative Nameserver to apply worldwide: 48 hours.
If you've made a change to your nameservers that doesn't seem to have taken effect, this is probably why.
If you change your Nameservers in Porkbun’s Domain Management console, this change can take 48 hours to fully propagate across the Internet. Waiting for the nameserver change is frustrating but there is sadly nothing we can do on our end to speed up this process. It is completely out of our hands. To check the Nameserver propagation of your domain, you can use a DNS propagation checker such as https://www.whatsmydns.net/ and select “NS” as the record type.