It could also be pyoderma or, if she has allergies or anxiety, a sore spot from licking her nose. Rafi has a spot under his nose exactly like this (healing up now) from the last time I went out of town. He was nervous and his nose ran the whole time.
Old Bitch survived cancer twice and was finally taken by osteosarcoma at nearly 12 years old. Discoid lupus was manageable and never a problem for her. It could be anything so I am glad you will go to the vet.