The winger picked up the issue during England's 2-0 victory over Albania, a match that marked Thomas Tuchel's debut as England manager.
Gordon, who came on as a second-half substitute, was involved in a challenge that left him in visible discomfort. At full-time, he was seen on the floor holding his hip, raising concerns over a potential extended absence.
Tuchel provided a brief update on Gordon's condition post-match but did not elaborate on the severity of the injury. Newcastle will now await further assessments to determine the extent of the problem.
"He looks injured," England boss Tuchel said.
"First of all I thought it's his stomach, but it's his hip and it does not look good. It's a bit worrying, yeah."
The timing of the injury is particularly frustrating for Newcastle, as Gordon is already serving a suspension.
The 23-year-old missed the Magpies' Carabao Cup final win over Liverpool last weekend due to disciplinary reasons, and his latest setback could see him sidelined for even longer.