Toddlers eye is super swelled out?

My 2 year old son woke up this morning witj what looked like a little bump on his eye brow area tonight his entire eye is swollen and it feels like he has a pea moving around in there?? What could it be? Im taking him to thw doctor tomorrow unless it gets to bad tonight but ive never seen anything like it I thought he bumped his noggin but now it looks super rougj. Its turning purple.