Why Is The Area Between My Nostrils Red And Sensitive?

hello, my name is Helen Bridges. This has to do with my nose the the area under it between the two nostrils. It has a red area that is sensitive to the touch. Yesterday, my right nostril was sensitive...and so I used a dab of MUPIROCIN ointment on the outside and around the rim of the nostril. the Mupirocin is 2%. Today the sensitivity is only in the area between the nostrils. What do you think is happening?