I had a very similar problem ... somebody had run a light fixture by drilling through an exposed ceiling beam from above during a past remodel. Then they pulled their ROMEX down through the hole.
Owners wanted to hole to go away, especially the wire.
Fortunately, there was additional wiring work adjacent to this mess ... and I located the wire which had powered the thru-the-beam-light. Re-routed the power to a new light, leaving the old one dead.
Trimmed the wire flat to the beam, then pounded it back up as far as possible. Used a plug cutter to cut an exact 3/4" plug and a Forstner bit to drill up into the beam. Glued the plug into the hole, sanded it off, stained to match.
Done. Now you know what YOU need to do!