Officials initially called only a blocking foul on Robinson and did not assess the technical on Allen until going to the monitor to review.
Robinson reacted to the contact immediately on the play, grabbing his nose in the process.
Allen then made two free throws before Joel Berry II hit the two foul shots awarded to North Carolina for the technical.
Allen finished the game with 14 points and was booed by the Dean E. Smith Center crowd throughout the game.
Duke suspended Allen for one game for a tripping incident on Dec. 22 against Elon.It marked the third time in the past year that Allen intentionally tripped an opposing player.
The Associated Press contributed to this report.