The Butterfly Effect

When Evan asks his cellmate to look at his hands for proof that he can time travel, he then travels back to when he was a kid and stabs his palms. He now has marks on his hands as proof. But if he got those marks when he was a kid he would have had marks on his hands when he went to jail, no? So the marks being there wouldn t have proved anything to anyone but Evan himself if you think about it.