Hammer coral bubbling, is this normal?

Hey, my hammer coral is bubbling really big on one head right where the mouth is. It is about the size of a dime big. It's been like this since Monday and I'd hoped it would fix itself. Does anyone know if this is a bad thing or if it will go away on its own. Is there a way to get it down? Taking a pin to it is the only thing I can think of but I don't think that would be good for the coral. The tentacles on the head that's swollen still appear normal.
It stays inflated overnight, if that helps to ID the situation at all. This is taken with my crappy camera and a flashlight. I will take a better picture of it tomorrow if it's still inflated.

Any help is apreciated.
Adam

 

Good, it's nice to know that other people have experienced this. If it is getting ready to split then even better. Thanks for the help guys.