My DD did the same thing on the coffee table two nights ago - massive egg came up straight away. I'm no medical expert, but as I understand it, you should wait half hour after a bump before letting them sleep (which you did) in case of concussion. You can google the symptoms but I'd be wary of any wooziness, funny walking, strange changes in pupil size, immediate drowsiness etc, strange talking if they're at that stage.
You might be better off posting in the medical conditions forum for someone with real knowledge to give you a better answer and let you know if you should take it further. Hope all is well.