User blog comment:Kir the Wizard/The Resolution of Flashpoint/@comment-2112031-20160530123111

If you rewatch the scene from the Season 1 finale, 2024 Barry warns his younger self not to interfere and then speeds off with his kid self. Eobard then grabs the knife and stabs Nora. In the Season 2 finale, we see the event again, 2024 Barry speeds off with kid self, Eobard grabs the knife, but is stopped before he can stab Nora.

Season 2 Barry arrives at the same time that 2024 Barry warns his younger self.