Making his first league start since September after missing most of the campaign with a serious ankle issue, Forrest had netted Celtic’s opener in the one-sided contest before pulling up in the second half.
He was immediately withdrawn by caretaker boss John Kennedy, who’ll now need to wait on the diagnosis before knowing if the player will be fit to face Rangers in the all-Old Firm fourth round Scottish Cup clash at Ibrox next week.
Kennedy told Celtic TV: “Just in the second half he felt his back really stiff and general tightness in his hamstrings as well. We’ll need to see how he is.
“I took him off straight away and I did the same with the other sub who’ve played a lot of games. Get them off and get fresh legs on.”