If a car door lock is stuck, first try lubricating the lock with special products, such as graphite powder in an aerosol or tube, as this is the easiest solution. After applying the lubricant, wait a few minutes, and try carefully moving the key around. If this doesn't work, apply the lubricant again.
Make sure the key to the lock is undamaged and that its parts aren't too worn-out. If there is damage, use the original key to unlock the door. Always use a duplicate key while storing the original in a secure place for such situations. If you don't have another key, order one from the manufacturer, make a duplicate, and use it.
Take off the door panel, and examine the rods, lock cylinder and assembly, making sure there are no broken or disassembled parts. When taking the door panel off, make sure to remove all the screws and clips, as you can break the panel if something is still holding it in place. When you feel the door panel has become loose, detach any wires connected to it, and remove the panel.
If the lock is still stuck, unhook the rod on the door motor to check if the key works. Install a new door lock motor if it does. If none of these methods work, call a locksmith who can open the car using special tools.