My Husband, Age 55, Good Health Has A Strange Thing

My husband, age 55, good health has a strange thing happening. His shin is sensitive to the touch. Even touching the hair on this area kills him. It's only a small area, say 4 inches by two. It felt like this yesterday, but he was actually able to run 4 miles. Then this morning it was fine. Now , a few hours later, it's seriously sensitive again??