I Slipped & Fell Backwards, Hit The Back Of My

I slipped & fell backwards, hit the back of my head on concrete, last second or two before contact were erased, I remember being about to fall, then looking straight up on my back. I waited a moment until the pain abated somewhat, then I seemed to be fine. Briefly thereafter someone noted I had a nosebleed, not a gusher or originating from any apparent point inside my nose itself. Its a on/off gradual leakage, accompanied by a mild headache. ER?