Civic LX 1996(?) - Door problem

I have a honda civic LX 1996 I believe, and there is a problem with
the door (left back door). It was working fine, then one day it
wouldn’t open from the outside, only from the inside. So few days ago
I thought that the small LOCK notch/lever on the edge of the door had
something to do with it. So I flicked it and closed the door, and now
the problem got worse and it wouldn’t open completely. Please help me
with this problem. Would I have to see a mechanic or is it something I
can fix at home?

 

The purpose of that little switch is to disable the inside door handle so
the kids don't jump out. If your outside handle was not working and you set
that switch, then you basically shot yourself in the foot.

The outside handle is engaged/disengaged by the main door lock. Make sure
the outside door handle is fully down/in and try working the door lock
button/switch on that door up and down. If its just stuck in some
mid-position you might be able to get it to fully unlock & then the outside
handle will work. If you should get lucky and get it open, disengage that
kiddy lock first thing before you close the door.

Ultimately, the inside door trim has to come off and the lock mechanism
inside the door needs to be examined/repaired.