Goals by Anthony Stokes and Kris Commons sent the Hoops to the top of the Scottish Premiership, but the victory was soured by the loss of Matthews, who was stretchered off with a suspected broken collar bone.
Matthews will miss Wales' World Cup qualifying double-header against Macedonia and Belgium and Lennon believes he could be sidelined for up to three months.
"Our initial fears is it could be a fractured collarbone," he said. "If that is the case we could be looking at three months.
"We don't know yet, we haven't had any word back from the hospital yet, that's where is at the minute.
"If that is the case then it puts a big negative on what is a great day for us."
Lennon felt that Keith Lasley's heavy challenge on Matthews was worthy of a spot-kick, but did not blame the Fir Park captain for the injury.
The Northern Irishman said: "I thought it was a penalty. He has taken his leg first and followed through on the ball - anywhere else that is a free-kick.
"Adam did the right thing, he got his body there protecting the ball. For me it is a penalty.
"It was maybe the way he landed. It could happen anywhere.
"I don't apportion any blame to Keith Lasley for that. Tackles are made in the game, people fall over awkwardly so there is no blame attached whatsoever.
"But it was a penalty, that is my view.
"We are waiting to hear now but the physios all believe it could be a bad one."