As an FYI, research the phrase in a couple of urban or slang dictionaries and you will discover the meanings vary from literal translation to a meaningless, raunchy suggestion of understanding "who's" the boss. Even "normal" words or phrases have countless connotations in today's world.
If the guy started unzipping his pants and blocking your escape, you'd have a stronger issue.
Just remember that customers can come up with sewage spilling out of their mouths too. Mgmt would probably take this into consideration, wonder what your reaction would be, and question your ability to deal with them.
For this reason, I wouldn't let a one-time incident become an HR complaint. And, if it were to occur again, I'd FIRST let the guy know that I'd appreciate keeping the discussion level and appropriate.