The problem may not be due to the injection. It could be due the posture during the pregnancy and later poor abdominal muscle tone after delivery. Low back pain frequently results from poor posture, muscle sprain, lack of muscle tone and strength. Take mild anelgesics with Antacid. If pain is not responding to regular anelgesics and muscle relaxants, then there could be something deeper inside, like a disc bulge or something pressing on the nerve. An MRI of the Spine will clarify the issue. If pain still persists then consult a Neurospine specialist.