Mitchell, who plays Boaby the barman, missed rehearsals temporarily after he was injured while cycling in Glasgow - less than three weeks before the start of the performance's run.
Writing on his Facebook page, he said: "Well that was a good trick, crashed bike and cracked ribs half way thru rehearsals and a 6 week healing period! Aaaaaarrrrrrrggh ! What an ---- !!!!"
But any fears that Mitchell could miss part of the show's lengthy run were dismissed by Still Game co-creator Ford Kiernan. Instead he will be strapped up and ready for opening night at the SSE Hydro on September 19.
Kiernan said: "We thought we were really in trouble when Gavin told us he'd broken a rib. After all, he's a really physical actor and we felt it would limit him.
"And a broken rib is really painful. We hadn't a clue what we were going to do.
"But he's been to hospital and been checked over and told he'll be okay."
He added: "Thankfully, he says he'll be fine on the night."
A month ago it was reported that a further 10,000 tickets were being released for the Still Game shows at the Hydro.
A spokeswoman for Mitchell said: "Gav has cracked a rib. He's taking a couple of days to rest up but will then be back in rehearsals.
"The show and Gav's role within it is unaffected and he's looking forward to opening the show on the 19th with the rest of the Still Game gang."