he surgery apparently was needed because of breathing / respiratory (choose correct term here) issues. Perhaps it was not just something "damaged" outside.
If you notice, Cena goes through the match just by breathing though his mouth (that's quite visible and noticeable), and not being able to breathe through your nose (if it was his case) is not a good feeling, especially when you're doing something very strenuous (like... you know... wrestling).

Both men worked through their matches. iirc Owens had his nose stitched after the match AND returned in the end of the show for a confrontation with Sami Zayn right? He ended up busting himself open again. If his injury was severe, the officials wouldn't allow him to pursue the storyline, even if he forced himself to do it. If he, in fact, showed up again, and had it bust open twice in the same night, and in the night after as well, it's because it was nothing as bad as Cena's.