Polyfilla Blocked Sink

[StupidWoman]

Finally after 20 years, I have a beautiful new kitchen. However today as I was filling in holes and sanding down the walls for painting, I washed a cloth in the sink with some of the dust in the sink and now the pop up plug will not work at all. It's something I did in my old sink without any problems and wonder if there is anything that I can do to rectify it or have I made a very costly error? Thanks for any suggestions.

[plumbbob]

The pop up plug ought to lift out so you can clean away any debris that gets trapped underneath. If it doesn't then something is wrong with the installation.