Blocked Sink

[StupidWoman]

As of last week, after 20 years of waiting I now have a beautiful new kitchen. Today whilst filling holes with polyfilla I rinsed a cloth with the dust in the sink and now the pop up plug will not work and I can see pieces of white obviously stuck underneath the plug. It's something I did regularly (and possibly stupidly) in my old sink and I just wondered if there is anything I can do to fix this. Any help would be greatly appreciated.