If using Corosync/Pacemaker and you get a "ghost" node (due to changing the hostname of a node, for example), the command to delete the node is:

cibadmin --delete --obj_type nodes --crm_xml '<node id="hostname" />'
hostname should be replaced with the name of the node.

You absolutely do want to remove these ghost nodes, as they can prevent elections/allocation of resources, especially if using a two-node cluster.