What can i do if my husband has lower back pain, what should i do?

Depends: Really need more information to answer this best. If this is new and severe, then he should be evaluated to be certain nothing serious. If chronic or milder, then a good evaluation for consideration of physical therapy or other conservative treatments is best. If he has not problems taking, simple analgesics like advil/aleve might be an option to get him to that appointment.

Back pain: The back pain can be caused by muscle strain, spinal stenosis, ruptured disc, nerve impingement ... The treatment depends on the cause of your pain. If your pain persists, you should seek help from a health care provider (pain management physician, rehab doctor, neurologist...). You might benefit from a comprehensive evaluation and treatment.