you didn't mention if his foot was swollen. and or has any red lines in the area. it could be as simple thing as gout. which is very painful. and common for his age. he would need further test to find the root of the problem.
my grandfather has been laid up with a foot problem: burning aches body-wracking pain has been going on for 20 days. he says it feels like "a worm is crawling around twisting inside of his[my] foot. " please help me i don't know what is wrong with him.