Here’s the exact exchange from Star Trek '09:
KIRK: There won’t be a next engagement. By the time we’ve gathered, it’ll be too late. But you say he’s from the future, knows what’s going to happen, then the logical thing is to be unpredictable.
SPOCK: You are assuming that Nero knows how events are predicted to unfold. To the contrary, Nero’s very presence has altered the flow of history, beginning with the attack on the USS Kelvin, culminating in the events of today, thereby creating an entire new chain of incidents that cannot be anticipated by either party.
UHURA: An alternate reality?
SPOCK: Precisely. Whatever our lives might have been, if the time continuum was disrupted, our destinies have changed. Mr. Sulu, plot a course to the Laurentian system warp factor three.
“altered the flow of history” in other words: changed history, not create a whole other universe.