2 months after tooth extraction and something is happening...?

Upper lower back molar was extracted about 2 months ago and the last couple days I have been working hard. Well, after I was all done working for almost 13hours I noticed where my tooth was removed it was raised.. like a half tooth sized sore. After an hour or so I swished some cold water around in my mouth and it seems to get worse and worse feeling like its about to pop. I was feeling with with my tongue when all of a sudden it felt like it came off my extraction site! I quickly used my tongue to move this thing out of my mouth and spat it onto my hand. It is white/yellow with 2-3 little black dots (maybe food) and smells horrible. It's no bigger then an eye drop mind you. After that I examined it and realized it was shell-like, and then washed it away. But now the sore feels like its swelling again. What is this? I haven't had one problem with this extraction site and took very good care of it post removal up until a month ago where I went back to normal eating habits and working habits. Not until today has it changed. Thoughts?