The Celtic captain was forced to quit Scotland's game against Cardiff last Friday at half-time after suffering excuciating pains.
Now he is facing a race to be fit for Tuesday's Champions League game against Barcelona.
The Parkhead manager said: "He gets an injection before games. It is just unfortunate he has this significant problem.
"The only solution, from speaking to the medical team, is a concerted period of rest.
"But he wanted to play for Scotland and we weren't going to stand in his way.
"He was feeling pretty sore even in the warm-up at Cardiff.
"He got through the first half and, from where I was, he looked pretty comfortable. But obviously he was in a bit of distress and had to come off, which isn't like him.
"The days after games is a huge problem for him in terms of pain and discomfort. If the medical team were to think it would be a long-term problem for him in the future we would shut him down automatically.
"We would not put his career or his long-term future in jeopardy. But the medical team seem to think he can cope."
Meanwhile, Lennon said contract talks with Gary Hooper remain on course. But he shot down reports linking the Englishman with a January switch to Liverpool.
He said: "It wouldn't surprise me if there are a number of clubs in for Gary because of the way he is, but I would poo-poo that. We are still in negotiations and I don't think we're too far away.
Lennon also sounded a warning that should Celtic decide to sell or players decide they want to quit the club, they will not be allowed to go on the cheap.
"If there are offers coming in, they will have to pay what we feel the valuation is," warned Lennon.
Negotiations are also continuing with Kenyan midfielder Victor Wanyama who has been offered an extension to his current deal.
"We are hoping to meet his representative again next week," said the Celtic manager. "We don't have to offer him a new contract, his (current one) still has a couple of years to run.
"But we feel it is a reward for performances he has put in since he came in the door."
