Hi... Sorry to hear about the fall... Don't worry about the pain .. it is due to sudden hit on the ground triggered spasm around the spine... Spasm will definitely be panfull when it's gets loaded up...so sitting standing for a long time...bending activities will all be painfully... I suggest you to ice the area in the back frequently...5-6 times atlaest in a Day for 15 mins.. Let him take rest if possible..otherwise let him have a soft lumbar support... Let him have a pillow support in the back while sitting... If u have Anti inflammatory medications prescribed to you can have them again .. consult a GP before popping up those... You will get better faster... Hope this information is helpful for you.. Revert back in case you need further clarification....