Scotland face Wales on Friday and Belgium on Tuesday week.
Mulgrew and Hearts goalkeeper Jamie MacDonald, who was stretchered off wearing a neck brace, both recovered well from the early collision.
On Mulgrew, who played on for 20 minutes, Lennon said: "He was a bit groggy, a wee bit fuzzy. He wanted to carry on, but I think he was progressively feeling a bit more nauseous, but he has been checked out and he is fine."
He went on: "We'll have to check if there is concussion or a bit of grogginess. There is no reason why he can't go with Scotland and come under their medical department and let them look after him."
Hearts manager John McGlynn allayed fears over MacDonald, who appeared to fall unconscious after punching away a cross from a crowd of bodies.
McGlynn said: "At half-time he was sitting up no problem. The doctor said he took 20 minutes to come round, but he checked him again and checked his eyes and he was okay.
"I'm sure he'll be observed for the rest of the night, but he is fine."
Georgios Samaras struck the 34th-minute winner through the legs of Peter Enckelman as Celtic recovered from a flat start when they could have gone behind as Callum Paterson missed Andrew Driver's cut-back from 12 yards.
Lennon was "delighted" to get through the game unscathed after their first Champions League away win on Tuesday.
He added: "The players have put in a massive effort this week and you could see that fatigue was starting to kick in a bit towards the end."
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