what does "if you were Pinocchio right now and we could saw off your nose and have enough firewood to last the winter" mean?

It means that the speaker is addressing a person he considers a big liar.

Maybe he's talking to a politician???

I assume you remember the story of Pinocchio.

Maybe not:

http://en.wiktionary.org/wiki/Pinocchio

That means when his nose grew with lies, he can just cut off his nose to make it short again and put it in the fireplace.

The phrase "if you were Pinocchio right now and we could saw off your nose and have enough firewood to last the winter" is an exaggerated way of saying that someone is lying or telling an unbelievable story. It refers to Pinocchio, a fictional character whose nose grows longer whenever he tells a lie. In this context, the speaker is implying that the person's nose is so long from lying that it could be sawed off, providing enough firewood (due to its length) to last the entire winter season.

This expression is a metaphorical way of conveying disbelief or skepticism towards someone's words or claims. It suggests that the person is not being truthful or is exaggerating to an extreme degree. However, it's important to note that this phrase is purely figurative and should not be taken literally.