weird bump

Okay y'all not sure what to do here. All of a sudden I have this weird ball like bump on the opening of my vagina. 2 days ago it wasn't there and now it is. My fiancé asked me what it was and I have no idea it is painful and is getting worse in pain. Anyone have any ideas? 
It's about the size of a gum ball or small jaw breaker... I'm freaking out a bit :(