WWE's Matt Riddle JFK Sexual Assault Claim Triggers Internal Investig

Matt Riddle claimed an NYC airport cop sexually assaulted him during a confrontation -- and while he seems to have taken it back, an investigation is now underway ... TMZ has learned.

The WWE wrestling star posted a shocking allegation Sunday, taking to IG to throw up a photo of a Port Authority police officer at JFK ... and attaching a scathing caption. He claims to have been touched inappropriately by this cop but doesn't go into too much detail.

What he does say is that he told this officer "no," but alleges the man proceeded to do something out of bounds to him anyway. FWIW, Riddle has since deleted the IG post.

Now, as far as what led up to this and what exactly went down ... we have some answers. Law enforcement sources tell us Port Authority officers got a call for a disorderly person who was deplaning, and they met him in the terminal. As it turns out, that was Riddle.

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