Inner thigh injection site?

My dad injects insulin in his inner thigh and was directed by a diabetes nurse recently not to. He prefers it there and to use the outside of his legs. He injects once at night. Full disclosure, he is not necessarily diabetic, he survived pancreatic cancer and had what is called a whipple procedure. As a result, he has decreased insulin production.

Thank you in advance for anyone's input. I tried to search the posts but wasn't able to find any specific mention of inner thigh injection sites.