2:15 PM PT -- Lachey has issued a statement about the situation on Twitter ... saying, "For the record, i was not kicked out of the chargers game for excessive 'trash talking'. no, that honor belonged to the guy in front of me!"
He added, "i simply don't appreciate someone turning around and putting their finger in my face. call me crazy, but that deserved a reaction."
Lachey also praised Chargers fans ... saying, "aside from a few exceptions, i had a great time hanging with Charger fans all afternoon. honestly, some of the nicest fans around."
Nick Lachey -- a HUGE Cincinnati Bengals fan -- was escorted out of the stands at the San Diego Chargers football game this weekend ... after security decided his TRASH TALK crossed the line.
It's unclear exactly what Nick said to piss off stadium security ... but after he was ejected, the former boy-bander actually BRAGGED about getting the boot, tweeting:
"Just got kicked out of the chargers stadium and couldn't be prouder! Go Cincy Bengals"
A short time later, AFTER Cincy defeated the crappy Chargers, Lachey tweeted again:
"Bengals win again. i'd talk trash to everyone in SD, but what's the point? you already had me kicked out of the stadium and you still lost."
As for the kid in the Chargers gear in the photo with Nick, he was just a random fan -- and after the game, the kid's dad fired off a tweet to Lachey:
"Thanks for taking the pic with my son and being cool to us. Congrats on the Bengals win!"
FYI -- you can probably expect MORE trash talk from Lachey this season, his Bengals are 7-5 and are tied with Pittsburgh in the race for the 2nd Wild Card playoff spot in the AFC.