Mood is a stupid phrase that people use on Instagram/Twitter/Snapchat.
I'd say the best definition of what it means would be "my current situation/what I'm doing or feeling right now". So my interpretation and how I would translate what he said is..."I'm hanging out with Johnny Football right now, I think that's pretty cool, so I'll take a selfie with him and show the world through social media" - mood.
It's in the same stupid phrase category as: Goals, fleek, turnt, bae, the struggle, and the most annoying basic b!tch thing you can possibly say "Yaaaas". All of those sayings should have died in 2016, but they didn't, so here's to hoping they do in 2017.