Cops Investigating Nikola Jokic Brother Punch Incident, Ask Fan To Come Forward

Law enforcement officials are actively trying to track down the man who got clocked by Nikola Jokic's brother on Monday ... with cops hoping people come forward to help with its investigation into the incident.

TMZ Sports has learned -- Denver PD has seen the footage of Strahinja Jokic punching a spectator in the stands after the Nuggets' Game 2 win over the Lakers on Monday ... but as of right now, no one has filed a report claiming to be a victim.

We're told police are reviewing the clip circulating social media in hopes of identifying the man ... but they're also calling on any witnesses or other people involved to step up and talk.

As we previously reported, Strahinja was shown on video hopping a row of seats at Ball Arena and striking a man following his younger bro's 101-99 win over L.A. ... which appeared to stem from a heated argument.

Nikola's brother, Nemanja, and wife, Natalija -- who was holding their young daughter -- were also present during the altercation ... although the latter appeared to try to diffuse the situation.

Nikola has yet to address the video.