Star Wars fans who watched the Clone Wars also suggest that this dagger might be the stand in for something called The Dagger of Mortis, which might be used as a weapon to kill Palpatine. Or if the coordinates on the blade lead Rey, Finn (John Boyega), Poe (Oscar Isaac) and the team to Palpatine, then the “map” may become a weapon. But man, are we in the speculation weeds here.
Article source: https://www.cinemablend.com/news/2486087/star-wars-fans-are-complaining-about-a-possible-spoiler-that-just-showed-up-in-a-tv-spot