Thanks for writing your query.
It will be helpful if you mention :-
1. The exact location of the pain.
2. Whether swelling is present on any part of foot?
There might be a possibility of soft tissue injury
of the foot.
An X-Ray foot (AP, Lateral and Oblique view) is needed to comment about any fracture
Fracture is usually associated with swelling along with the pain.
Advice him for rest. Cold
compress will help in relieving pain.
You can apply locally pain relieving gel and apply elastic bandage
Pain killer can be given after getting him examined by an Orthopedician.
I hope this is helpful to you.