This sounds like planum nasale hyperkeratosis. Kerasolv was the product of choice but it is no longer on the market. Some people have had success with Corn Husker's Lotion, and others by applying straight propylene glycol to the affected area. A prescription product -douxo seborrhea spot on - is applied to the affected area once weekly. Your vet should be able to help you with this one. The former two you should be able to find in the local drug store.
I hope this is helpful. Please push ACCEPT and thanks!