North, 20, was one of Wales' stars as they claimed a Grand Slam during last year's Six Nations however he was carried off after 64 minutes on Friday after a blow to the head and neck.
With Wales' Six Nations opener kicking off in less than a month's time on February 2 against Ireland the injury will be a blow to interim coach Rob Howley's plans.
Wales and Scarlets star Rhys Priestland has already been ruled out for the entire Six Nations campaign with a torn Achilles.
Scarlets were on the wrong end of a 47-17 hammering in the clash at Ravenhill but backs coach Mark Jones admitted he was in the dark about North's fitness.
"I only know what I saw on the replay," he said.
"He's had a knee to the head and he's struggling with some head and neck issues."
While North joins Priestland on the treatment table it is among the forwards that Howley faces his biggest headache with no less than eight players, including RBS 6 Nations Player of the Tournament Dan Lydiate, sidelined.