*NSYNC's Chris Kirkpatrick Breaks Hand In Celebrity Softball Game, Keeps Playing!

Chris Kirkpatrick of *NSYNC was totally Pete Rose'd in the middle of a celebrity softball game ... getting leveled at home plate and breaking his hand in the process -- but somehow, the dude kept playing through the injury!!

TMZ is told ... the musician was one of several big names invited to participate in the Rock 'N Jock fundraiser for Folds of Honor in Nashville on Monday -- and at one point in the friendly competition, CK proved just how tough boy bands can be!!

The moment went down in the third inning ... when local radio host Jeremy Loper rounded third base and headed for home.

Kirkpatrick was protecting the plate, but Loper was out for blood (quite literally) ... pummeling his opponent as he tried to earn a run.

In the clip of the aftermath, Kirkpatrick is shown hugging Loper to make sure he knew there were no hard feelings ... but it's clear the singer can feel a bit of pain when he daps up another dude -- 'cause he quickly pulls his right hand back to his side.

As for Loper, he showed off his own issues -- with both his knees oozing with blood as a result of the play.

We're told Kirkpatrick initially thought his hand was just sore, so he toughed it out and played the rest of the game ... but when the pain lingered a bit, he got checked out by a doc -- and sure enough, he busted his paw.

Despite the injury, it looked like a successful night -- raising $408,000 for military families ... with names like Deandre Hopkins, Taylor Lewan, Charles Esten and Ross Chastain getting involved in the fun.

Naturally, there was also a moment where Kirkpatrick hopped on the mic and gave the whole stadium a rendition of "Bye, Bye, Bye" ... so he really was putting it all out there for his team!!

Folds of Honor Tennessee Executive Director Jenner Kreifels raved about how the event turned out ... telling TMZ Sports, "Over an hour rain delay for this year's Folds of Honor Tennessee Celebrity Softball Game, but the players, board members, sponsors, and the fans stuck it out for a beautiful night!"

"Over $400,000 was raised for deserving military and first responder families. One of the highlights of the night being Lee Greenwood performing his hit 'God Bless the USA' live during the 7th inning stretch."

Just by looking at the pics of the event -- shot by Nicole Murphy -- it's clear Kirkpatrick wasn't the only one giving 100% ... as all the celebs put their 100% into the competition.

"Thank you to everyone who helped make this year’s Rock 'N Jock game a huge success," Kreifels added.