Tarek El Moussa got into a physical altercation in Vegas — and while he walked away with a citation, sources close to the HGTV star say he was stepping in to defend a family member.

A spokesperson for the Las Vegas Metropolitan Police Department tells TMZ … the “Flip or Flop” star and another male were involved in an altercation last Thursday at The Palazzo at the Venetian Resort.

Witnesses who were at the scene tell TMZ … Tarek delivered a brutal knee to the man’s head, knocking him out cold. One witness called the incident “bad,” saying the other guy looked seriously roughed up.

It’s currently unclear what started the fight, but we’re told it escalated quickly. Cops took a crime report and cited Tarek for battery, but did not arrest him. We’re told the alleged victim refused medical attention.

A source close to Tarek tells TMZ … he was stepping in to defend his elderly father, with the source suggesting the confrontation was sparked by the man getting out of line with his dad.

Tarek’s wife, Heather Rae El Moussa, was with him at the time — but we’re told she had no role in the scuffle — sharing some pics and clips from the family’s Vegas trip on her Instagram.

Blake Lively may have thought her legal drama with Justin Baldoni was finally behind her after her stunning court victory … but JB’s lawyer says the case is just getting started.

As you know … Blake scored a big win Monday when a judge tossed out the claims Baldoni made against Lively, her husband, Ryan Reynolds, and the New York Times in a $400 million lawsuit.

Baldoni accused them of defamation over an article about Justin’s ugly feud with Blake behind the scenes of their 2024 film, “It Ends With Us.” He insisted it was all part of a smear campaign against him.

In a statement released Tuesday, Baldoni’s attorney, Bryan Freedman, fired back, telling TMZ, “Ms. Lively and her team’s predictable declaration of victory is false, so let us be clear about the latest ruling. While the Court dismissed the defamation related claims, the Court has invited us to amend four out of the seven claims against Ms. Lively, which will showcase additional evidence and refined allegations.”

Freedman went on … “This case is about false accusations of sexual harassment and retaliation and a nonexistent smear campaign, which Ms. Lively’s own team conveniently describes as “untraceable” because they cannot prove what never happened.”