'Real Housewives of Miami' Star Punches Homeless Man In Nuts -- Cops Looking Into Video

"Real Housewives of Miami" star Peter Rosello -- the son of housewife Alexia Echevarria -- appeared to have assaulted a homeless man on camera this week, then posted the video online ... and now, police are looking into the footage.

The video was shot in South Beach Monday night -- you can see Peter looking into the camera, and introduce the "prank" by saying, "Punching a hobo in the nuts."

Peter then walks up to a sleeping homeless man and tells him, "I was gonna give you five dollars" ... before dropping his fist into the man's crotch.

Peter and his cameraman then run to a nearby car and make their escape.

A rep for the Miami Beach PD tells TMZ, the department is currently trying to identify the victim in order to open an investigation.