My 92 Y/o Father Who Has Been Is Good Health

My 92 y/o father who has been is good health is now obsessed with his fingers/hands. It started in Feb. He thinks there is "wax" on them and is constantly "peeling" the wax off. He also thinks there is wax in his ears,nose, between his toes. As a RN I have tried to explain there is no logic to this. He does not believe me. This started rather suddenly. Do you think he had a CVA or is it dementia? He otherwise is behaving normally.