Factual error: Chucky blows out the pilot light in Eddie Caputo's house and, mere minutes later, there's enough gas for a single gun blast to then cause the whole house to explode. 1) It would take hours and hours for enough gas to fill up that house to present a safety issue; 2) By that time, Eddie would have unmistakably smelled it; 3) A gun blast wouldn't be enough to ignite that gas anyway.
Factual error: The movie appears to take place in the winter but when Andy goes into his mom's room with breakfast at 6:30 in the morning it is light outside. At that time of the day it would still be dark outside.
Chosen answer: This isn't a mistake. John made the voodoo doll himself. When Chucky said he was "prepared" for it, he meant that he was prepared to do whatever it takes to get information from John about his being wounded. Even killing him as we see.