Its probably nothing to worry about, but give your OB a call... As long as baby is still moving (even a little) there most likely isn't anything wrong.
Baby is probably fine but I would just give the OB a call to be sure.
Call your OB if you're concerned, but your baby has plenty of padding and protection in there. I would absolutely not even consider going to the emergency room for that. For one, it's not an emergency - heart attacks and broken bones are emergencies, not being bumped into. Therefore, it's a waste of time and resources for the people working in the emergency room, and a waste of money for whoever is paying your medical bills. And two, emergency rooms are often full of sick people. You're more likely to get sick while sitting in the waiting room than just about anywhere else you can go - you don't want that. Everything will be okay, don't worry. But call your provider if you are really worried about it.