Little Torch Regulator Knob Stuck

My Little Torch O2 regulator is stuck and I can’t get it to turn
either way. It’s the black plastic On/Off knob that says “Do not
force Knob” on it, and I have the torch that connects to disposable
O2, Propane bottles. Does anyone know any tricks for getting it
unstuck? I tried gentle taps with a mallet, and putting the thing in
the freezer for a few minutes, but no luck. I don’t want to buy a new