I have a Cordon apple tree and so does my neighbor. His fruit ripens and is picked, but mine is still green one month later. Why does it take so long for my fruit to ripen? The apples are full size and not growing anymore, and soon start getting brown lines inside which I see when I cut one open.
The fruit stops ripening because the tree is stressed. The damage you describe sounds like it might be apple maggots, which would stress the tree. Here is more information on apple maggots: