Hmm, is that actually how it would work? Even if Turkey is the aggressor and attacks Greece, they (NATO) wouldn't help Greece because Turkey is also in NATO? That sounds a bit mad, Lol. Still, I don't think Turkey has any serious intention of attacking Greece and it's just Erdogan being a dick as per usual and hamming things up for the elections, once they're over I expect him to shut up.
It's never been tested (and hopefully never is) as to what happens if one Nato member attacks another. I'm theory Article 5 would apply to the nation under attack, but the aggressor could jam up the political machine (and likely would in the lead up to the attack). Presumably though the aggressor would be turfed out of Nato