Recently iv noticed that it really smells and iv been cleaning it out with cotton buds and a yellow-ish substance comes out (similar to ear wax but it smells really bad) So yesterday i was just fiddling about with my belly button and i could see there was something actually inside. So i sterlised some tweezers and tried to pull the thing out but i couldnt. So i started to proud around my belly button in a sort of massage type of way, and right before my eyes this hard substance thing (about the size of a 10p piece/a quarter) popped out of my belly button! I was in disbelief...it didnt hurt as it came out, it literally just slid out as if it was the most normal thing in the world. It was really hard, like it couldnt be squashed between my fingers. It wasn't gooey or wet, it was dry and hard. It smelt very bad. I ended up breaking it up with my tweezers and it was brown and 'fibrous' inside. I flushed it down the toilet.

Any ideas as to what this could be?

HELP?