About 30 minutes ago, I was bending over to try to pick up a paper bag (light weight). I heard a cracking sound on my back. Then I felt this pain on my lower back. I tried to lie down facing up for about 20 minutes and I feel better. I have to get up, walk slowly as I still feel some pain but it is not as bad. As I moved, at certain position, I still feel the pain and I have stop. May I know if this could be serious problem? This is the first time I have experience this. I am 45 years old male.
Hello. To Have pain after getting crack, does not mean that you have a serious pathology. Muscle tear is likely diagnosis (pathology is not important). In my opinion Diclofenac 50 mg thrice a day can be taken for treating you pain.  The application of local heat too will relieve your pain. If after 15 days start taking diclofenac no improvements, is needed to realize a radiography. Please consult your local doctor for a prescription. I wish you good health.(If the answer has helped you, please indicate this)