It sounds like a pretty nasty fall. I would be concerned that you might have a fracture
and so would encourage you to have an Xray of your back where the pain is. If this is normal then it is very reassuring and you could assume that this is a soft tissue injury
which should improve over the next 2-3 weeks. You could take anti-inflammatory drugs in the meantime to help with the pain - if you have no contraindications to this type of medication.