We had a scare like that. My son fell and cracked into the door frame and got an instant egg on his head. He cried for like two minutes and then seemed fine. I took him to the emergency room to be sure. They checked him out, but were not too concerned. They said that if he started throwing up or had blood comming out of his ears or nose, or if he remained fussy to bring him in.
Things like that can be really scarey, but they told me that babies heads are specially designed to protect the brain from the falls that they have to go through to learn to walk, etc... They said if the same thing had happened to an older adult, there may have been brain damage, but young children can withstand more. It never hurts to have them checked out, though if you feel something could be wrong. Go with your gut.
The after affects looked horrible! The bump drained into his eyes and made him look like he had two black eyes. Man! The looks I got from people. One lady even asked him once if mommy had hit him! GGrrrrr....
Hope your little one is OK, it is always hard to see babies get hurt.