Hello and welcome to ask a doctor service. I reviewed your query and here is my answer. Is it localized to lower back or the pain radiates to other location as well? Were you hit on the flanks or center of back? There are almost minimal chances of your kidney injury, if your kidneys were damaged, you would have problem in urine as well. It looks like your muscle or bones have been causing this pain. You can use pain killers for that. But you need to consult an orthopedic specialist for this. Hope i answered your question. Feel free to ask more if you need further assistance. Thanks.