"I can't describe in words how gutted I was with the injury because I want to play as many games as I can and we're in a good position at the moment," Kightly told the Express & Star.
"My first thought was that I might be ready for Colchester United and then, after 48 hours, it looked a little bit worse.
"I was a bit upset on Tuesday because that was when we thought it might be more serious but I had the scan on Wednesday which wasn't as bad as we feared.
"I'm still going to be out for a bit but it could have been a lot worse, and hopefully touch wood, I can get back fit in a few weeks."