Bathroom waste

[tersandra]

Hi, I've unscrewed the bathroom waste and unfortunately when I went to screw it back in it won't do it, so I had to remove the panel to take a look and underneath there is a black pipe the top of which is like an open thing and the screw which should go in the middle of it won't do so because the plastic thing is split.

How do I sort this out please, do I need to remove the whole thing and buy a new one, do I need to then mastic it in or do I need to call a plumber?

Many thanks
Sandra