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.
Continuity mistake: When Andy makes his mother breakfast in bed he brings in a glass of orange juice but over the course of the scene of him and his mother talking it changes to a much lighter colour. It could have been switched with a glass of milk or cloudy lemonade but it's probably just the same orange juice that's been watered down over multiple takes.
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.