Hi welcome to HCM I have gone thru your query regarding back pain after an injury . It is a matter of concern . Dear three weeks time is quite long time for recovery of injury from a fall .It seems some muscle or nerve your lower back has been injured by the jerk when you fell . For instant relief you can take Homeopathic Arnica 30 /3 doses /at half an hour gap and apply few drops on painfull area . Gently massage or rub the area to relieve pain and encourage blood flow. Do not massage the injured area if it causes pain. If swelling is gone, apply heat. Use a warm pack or heating pad set on low. can also begin gentle exercise with the aid of moist heat to help restore and maintain flexibility. Avoid sitting up in bed, sitting on soft couches, and twisting or sitting in other positions that make your symptoms worse. Back pain often gets better when you gradually increase your physical activity. Try to get back to your normal routines and activities as soon as possible. Resting and not doing anything may actually increase back pain or make it last longer Sleep on hard surface . Do back bending yoga postures as Bhujangasan , Ushtrasan , Vajjarasan ,bend back sitting on Vajjarasan never bend in front .It will worsen the pain . Lie on your stomach if it does not increase your pain .Then do Shallabhasan -stretch your arms and legs in air and head up ,balancing on stomach . Deep Breathing will further strengthen yuor back and relieve from pain . Take a level spoon of turmeric powder + almond oil with a cup of hot milk at bed time and in BF for healing internally relieve pain , Balanced Deit containing all essential nutrients - Fiber , protiens , Vitamin D,C, minerals , fish & fish oil ,Nuts , lot of water all will help strengthen your immunity and help fast recovery and to achieve over all sound health , Make sure to get sound sleep and avoid fried fast foods , tea coffee ,alchol , smoking constipation , worry , mental stress , anger . which may delay the recovery . consult your ortho physician and get checked for any serious injury . Hope this helps solves your query .Take care .All the best Don t hesitate to come with further query if you have any .