Did you try to update the Splunk Web values of the Splunk Server Name?
You can do that through Splunk Web (Click on Manager, General settings). And I have attached the link to the documentation explaining the different parameters you can use for your reference.
Change the default Splunk server name
The Splunk server name setting controls both the name displayed within Splunk Web and the name sent to other Splunk Servers in a distributed setting. The default name is taken from either the DNS or IP address of the Splunk Server host.
via Splunk Web
Log into Splunk Web as the admin user.
Click Manager in the top-right of the interface.
Click the System settings link in the System section of the screen.
Click General settings.
Change the value for Splunk server name and click Save.