Howard Stern Staffer Benjy Bronk -- Flirting with a Finger in His Butt ... Says Wanda Sykes

'Howard Stern Show' writer Benjy Bronk got a rude awakening from Wanda Sykes, who warned him he's getting dangerously close to an unwanted ass inspection from a stranger.

We got Wanda and Benjy outside the Sirius XM building this morning in NYC -- and she started ripping him about his big wager with Howard.

If you haven't heard ... Benjy has to drop 37 pounds by July 21, or Howard's bringing in someone to, uhh ... examine Benjy's prostate. Oh, and he'll have to make out with the mystery guy too.