Never believed too much into Nick being guilty of anything outside of poor choices
and bad timing.
My gut tells me he walked in on Vinny using laptop at the party(Vinny has shown he can come and go as he pleases) and is protecting Vinny having used the laptop when the cluck went out(bro code of silence or loyalty to Vinny. No one ever asked Nick specifically if he saw Vinny using laptop).
Whether Vinny is the one who did the cluck post is still debatable as we don't have a real motive for it.
The only person I see wanting to potentially hurt Cathy is Jade(it seems to be intimated her husband has messed around with Cathy) but how that would work would be weird.
(Jade hiring Vinny/Nerds to get dirt on Cathy?)
Fun times of speculating.