Hi.
The repair is not difficult. I do not think that you can unlock it with your finger, usually a stuck lock is quite hard to move.
Check the latch mechanism under the trunk lid. If it looks like the latch is rotated toward the left hand side, then the latch is stuck in closed position. That is the reason why the latch does not close.
Spray a good amount of WD-40 on the latch. After lubing the latch try using the key while at the same time operating the trunk opener switch inside the car (ask someone else to help you).
If the latch is damaged or if it does not unlock, or if after unlocking it stays stuck open, then you will need to replace the latch, which is not a difficult operation.
Here instructions:
- Unplug the battery ground cable.
- Disconnect lock cylinder rod and the release cable from the latch.
- Undo the latch screws, disconnect cargo lamp harness.
- Remove the latch.
- Connect cargo lamp harness to the latch and install the new latch.
- Tighten rear compartment latch bolts to 10 Nm (89 lb inch).
- Reconnect release cable and lock the cylinder.
- Connect back the battery GND cable.
Here a diagram, click on the picture to enlarge: