I'd have to look to say for sure, but it seems to me that the knob is screwed on the shaft and a nut is used to secure it from backing off. Perhaps the nut has come adrift.
The headlight tool is definately good to have around though!
1957 Austin-Healey 100/6 Wine Red
1961 McCulloch R1 go-kart Screaming Yellow
1999///M Rdstr Cosmos Black
2001///M Rdstr Steel Gray
2011 X5 35i Sport Deep Sea Blue/Cinnamon