Please help. Driver side door has dropped and won't lock, all others work fine

[randomist_legend]

I have a Clio 5 door 2003 model mk2 and the door has dropped. It has probably dropped 1 or 2cm or so but basically it now bangs on the actual door hinge thing (the black rubber circular cylinder sort of thing that the locking mechanism locks into which is screwed onto the door frame) that black circular thing has also started to become a little corroded like you can see the wear, it’s not smooth it’s as if someone has put a tight ring on it and squeezed it and it’s imprinted because of the door locking mechanism rubbing on it. Do I make sense? So basically now the door isn’t locking either. When the car is locked, all the other doors and the boot are secure but this door just opens as if the car is unlocked and of course you have to push the door in hard for it to shut properly or slam it hard otherwise it just bangs on the black cylinder thing that the locking mechanism goes into... because the door has dropped it doesn’t fit onto the black thing and it’s sort of misaligned. This probably makes no sense but I’m sure someone will know what I’m talking about. I want to know how much it would cost to fix it by whatever the cheapest solution is?