This is a sweet "Hello, how are you" nuzzle from your cat. Cats greet each other in this manner (and we all know how dogs greet each other, ahem!)

Cats tend to explore their world with their sense of smell.. I recently had an infection in my outer ear canal, and my kitty would climb me like a mountain, stick her nose in my outer ear, and sniff vigrously, and then climb down with a most concerned expression on her face. *priceless*