Something is stopping the boot catch from completely locking. I think the continuous bleeping is from the lock managemnt system, telling you trhe car is insecure.
Have a goodly rummage round the boot closure fo rany obstructions and in and around the lock area fo ranything thay may be blockiking it.
Have you done a Google search for Micra boot lock problems or Micra boot catch problems? There may be a few mentions on dedicated motoring forums if its a common problem
Boingo - couldn't resis it. I did a quick Google search and got a pageful of hopeful results. The $64000 question is: Why didn't you search? It was Sooooo easy!
Anyway. gripe aside. try these for inspiration:
http://www.3dlabellingsystems.com/pages/micra_faulty_boot_switch.html
http://www.theanswerbank.co.uk/How-it-Works/Question1131420.html (See Needawin's post about one screen scroll down)
There was even a thread ON HERE! http://howtomendit.com/answers.php?id=165600
http://www.diynot.com/forums/automotives/nissan-micra-boot-lock.302357/
Now you've seen what Google can produce - please use it!
Arthur, February 2015