Hi there
It sounds like ankle sprain to me. And you can go for
R=give rest to foot as much as he can
I= ice pack for 15 minutes every 2 hrs
C= compression by crepe bandage after applying volini gel or any other anti inflammatory cream available
E= elevate the affected leg on two or three pillows while lying on bed or sleeping.
Next Steps
might need an x ray for further investigation
Health Tips
take him to any orthopaedic doctor asap