When I lived in Germany, the stairs into the cellar were concrete, and because they were out of sight (...out of mind), they weren't carpeted, so inevitably they were often cold and slippy, especially when walking bare-foot. As it happened, in our stay there, every member of the family at least fell some way down these monsters. My day came when I was about six, and I was stupidly running through the house in a hyper-active moment. As I turned to run down into the cellar, I slipped, and slid ony my back all the way down the steps into the cold, dark cellar, screaming and crying my eyes out.
The pain was excruciating - and I think it's actually my first ever experience that I remember of pain. I had a sore back for a good week, but there were no other after-effects. However, I've since had a few mild back problems that may or may not be associated. My mum suffered a far worse fall down the steps and has since been diagnosed with a minor nerve problem in her lower back. Basically, falling down the stairs can either be very serious or it can't. I'd advise seeing your doctor about it, just in case, especially with the after-effects you're experiencing.
It sounds a little silly, but most people will fall down the stairs at some point. I've averted disaster a few times. They're surprisingly very dangerous for something so common, and even though I am fit and nimble, I still find the concept hard to grasp at times. The worst feeling of all is when you take a heavy step forwards towards the stairs and you sort of topple, your heart skipping a beat inexplicably as it anticipates a fall. I've done that lots of times, but I think it's much more nervy, and considerably worse than it should be given the aforementioned fall.
Stairs - I hate them. Give me a ramp and carry me up it.