Hi. Sorry to hear about problem of your husband. Although a little more info may be needed to reach to a conclusive diagnosis (like exact localization of the pain, severity, does it feel to be of muacular/bony origin, is it present at rest or associated with movement, pain increased/decreased in any special movement/position). However lets workout with the information available. As you said injury sustained during attempting a back kick , it seems that the problem arose due to excessive stretching of muscles/ligaments or tendons. In either of the conditions, basic requirement for the treatment is bed rest along with use of anti-inflamatory/analgesic agents. So here is the plan. Ask him to take bed rest. Consult your primary physician for a prescription of pain killers if they are not available over the counter in your locality. You can visit an orthopaedic surgeon for confirmation of diagnosis. Wishing you and your family the best of health. Regards