I think he was just extremely happy to see her again and know that she was okay. You have to keep in mind that in this point of the story, her day could come at any time, and it's really ambiguous to him what could happen to her. I think, should certain other events not have happened, once that shock wore off he'd feel bad and apologize, but he knows Xion can handle herself well in a fight so he wouldn't agonize too much over it.