Bump on your dog's nose can be due to some inner swelling. Another reason can be; your dog is hit by some solid and hard thing that has caused this bump on its nose. Examine it properly and if you find an injury there, apply Pyodine on it. It will heal the wound and will create resistance against any further infection in it.
Another reason can be skin infection due to dust. Keep your dog clean by giving it bath with some medicated lotion. It will also help curing the infection. There are also chances of a disease, Discoid Lupus. So, it's better if you consult veterinary doctor as well.