A source close to John Cena gave the following comment to Hollywood Life about Cena’s reaction to Nikki’s engagement :

“John is very happy for Nikki and her engagement. He is very happy that she has found someone that treats her so amazingly well.

Nikki was a very important part of John’s life so it does remind him of what they had, and he is also reminded of his proposal to her at WrestleMania a few years ago, but he also has believed that they have both grown from their relationship, and they both have moved on.

He knew it was going to happen at some point so instead of taking it in any weird way he is wishing for the best for her, and he only wants to send great vibes her way and hopes she gets everything she deserves with her life with Artem.

He knows she deserves all the good luck and love she is receiving, so he is happy.”