I have a hard bump on my face. When I squeeze it a kind of extremely thick pus maybe (I'm not sure what it is) comes out; it smells terrible. After I squeeze it and there's no bump there it'll be fine, but after a while it will come back and I just squeeze it again. What is it and how can I get rid of it? It's not large, about the size of a normal pimple, or red/inflamed/swollen/etc. It's not painful either