The 21-year-old was forced off during the Tigers' 2-1 win over Middlesbrough last Thursday - a game that saw him open the scoring with a fine free-kick.
But that will be the midfielder's last appearance for the Championship club this term after the full extent of his injury was revealed.
Hull boss Grant McCann said: "Looking at the scan, it's not a nice one for him. We're gutted for Herbie because he's had no luck since coming here.
"He picked up the injury in training when no-one was near him before lockdown and now he's pulled a hamstring.
"We'd love to have him back with us next season. He's everything that we need and everything that I like in a player - with his energy and bravery.
"He can score goals and he's calm on the ball as well. We'd love to keep him here next year."