Hello madam good evening.i am very happy to see your concern regarding health of your father in law. Ok now let me come to the point. What you have mentioned is going in favour of muscle sprain.but not exactly.
Next Steps
you give him plenty of water and fruit juices. give him hot water or salt application or foamentation. ask him to take rest. see it for 2-3 days.
Health Tips
if there is no improvement or if pain increased take online consultation with me. I will see into it and try to solve the problem. ok