Remove the ESXi Host from vCenter Once removed, ssh to ESXi and update the FQDN hostname.

To rename a VMware ESXi host:

Log in as root to the console of the ESX host.
Using a text editor, change the name and domain name, if applicable, of the host in these files:
 
/etc/hosts
/etc/sysconfig/network
 
Run this command:

esxcfg-advcfg -s ESXi_FQDN /Misc/hostname
where ESXi_FQDN is the new FQDN hostname for the ESX host.
Reboot the ESX host.
Join the ESX host to VirtualCenter/vCenter Server and clusters.