What Causes Back Pain After An Injury?

Hi - Yesterday afternoon I had the bright idea to walk down a railing at my brother's school. I only got a few steps down when my feet slipped out from under me, I landed on the stairs on my lower back on the right side above my pelvis and below my rib cage. I can still walk but I have to keep my back upright. The pain is only excruciating if I bend over to touch my toes or rest my back against something. I dont think I broke any bones but am unsure and I would go to see a doctor but dont have health insurance. What do you think I should do? I'm hoping it's just my muscles at this point since I definitely have to work tomorrow.