If he says it will grow now, it will grow after he says it, because he lied, and it grew after he said it, which is not "now", so technically, he lied, and his nose grew.
If your weatherman says that it's going to rain on friday, and it doesn't, was he lying? No.
Was he telling the truth? Not really either.
Predictions are neither truth nor lie. Therefore nothing would happen to our dear wooden friend there. (Nor would he bleed, as the content portrays, since he's made of wood at that point and thus has no blood.)
Predictions can turn out to be true later, but without knowledge that you are going to be correct or going to be incorrect, I still contend that you cannot be lying.
The way I'd explain it if he says "my nose will now grow" and it doesn't, he didn't really lie, he was just wrong, so nothing would happen.
But then after that he knows nothing will happen, so he would be lying, in which case it's ****** once more.