Childermass isn't up to moving around just yet but he can give Lambert a long-suffering look when he brings up the knife, around a bunch of people who don't know about the knife. It probably won't matter for long if he's going to use it for what he's thinking he will...

"Fine. Just... give me a minute."

He'll struggle back to his feet eventually, by around the time the non-shocked members of their little party have cleared the three technicians away.