From the vCenter Web Client or ESXi Host UI it is not possible to expand the NFS datastore as this is a file level datastore. Hence ESXi hosts does not have privileges to expand the NFS datastore and we cannot see any option to expand the NFS datastore via the vCenter Web Client or the ESXi Host UI.
Engage your storage vendor/Admin to expand the datastore from the storage array.
Once the datastore has been expanded, rescan storage from vCenter to reflect the newly expanded size.