That was Colonel Worf, the ancestor of the Worf featured in Star Trek: The Next Generation. Note the difference in his cranial ridges.
Michael Dorn was playing a member of the House of Mohg, an ancestor to Worf.That wasn't Worf; it was one of his ancestors.
It wasn't the Worf from TNG it was his grandfather Colonel Worf. As seen with the Duras family in TNG and ENT a name stays in a Klingon family and will be used through the generations