I personally think you don’t have to go down this path at all.
Let’s examine the statement: “My nose will grow.” This is a statement that is vague at best as far as the time strata in which it refers to. The only thing that needs to be true for this statement to be true is that: “Sometime in the future, my nose will grow.” Vagueness aside (one could easily assert that you could change the statement to say, “My nose will grow at exactly 4:33pm today.”) this statement has a truth value, but truth values are either true or false. A lie is neither of these. A lie depends on intention.
One certainly would not say I “lied” if I said, “I’m going to the store today after dinner,” if I, 5 minutes later, got shot by the mafia and perished. Nor would you accuse someone of being a liar if they incorrectly believe that 1+1=3. They’re just moronic. A lie depends on knowing the truth of a proposition, and using that information to deliberately mislead. In this case, Pinocchio does not know the veracity of his statement and thus could not lie. He may believe falsely or truly, but he’s not intending to mislead.
By this line of reasoning, Pinocchio neither has to be omnipotent or be a walking contradiction. He’s just a puppet that wants to be a real boy.