What Causes Joint Pain While Walking After Falling From Stairs?

I damaged my big toe just over 3 years ago when pregnant. I fell down the stairs (on my back) and my toe took the force as I tried to stop myself falling. It turned black around the joint from my big toe to the ball of my foot. I have had pain around the joint on a daily basis ever since. I had an x-ray a year ago, but nothing showed up. It effects how I walk as I can't bend it fully. And hurts no matter how comfy the shoe I'm wearing.