Spock Prime from the classic Trek timeline inadvertently helped create the Abramsverse while trying to stop the supernova shockwave. It's no different from past alterations of history except that the Abrams timeline persists and we continue to follow the events within it.
Not seeing the problem other than "convenient excuse to have Leonard Nimoy in the last two films to get more butts in the seats," but again - why is that a problem? Spock Prime helps tie the two timelines and realities together. He's a welcome facet of and addition to the new films.