What can I do if my carpenter cut a door too short?

You might also consider raising the floor slightly if it's practical—it could create a better fit for the door. Just make sure that it doesn’t affect anything else in the room, like the trim or adjacent flooring.

Honestly, this seems like a job for the carpenter who did the work. If they messed up, you should reach out to them and ask for a fix—they should be responsible for correcting their mistake!

One option could be to use a door stretcher, which can help lengthen the door to fit properly. It’s a specialized tool, but it can work if you're in a pinch! Just check online or at your local hardware store to see if you can rent one.