I keep getting mild pain in back left corner of head and runs to my nose sometimes. not sure what it is. is this where the pituitary gland is located?

No: Whatever it is, it has nothing to do with your pituitary. "Pituitary" comes from the Greek word for "pea" because it's about the same size and shape. I've never heard of a pituitary problem causing pain, unless a tumor swelled it to the size of a golf ball; in which case you'd have a lot more symptoms and a neurosurgeon would be planning to drill a hole in your head.