Sometimes a caulilower looking sore can come up on there noses.It can be caused from yeast on the nose or allergies or they can appear with age.Nasal planums are usually not painful unless the scabs start to rub off and make the skin inflamed.There is a medicine called Kerasolv that your vet can give you to treat it if that is what the problem is.Also if the scab appears to be thick you can use a warm washcloth to help with the thickness of it and loosen some of the scab.Just dont pick at it though.Good luck and take care.
It would be hard to say without seeing it. It could BE a wart....it could be a cyst, or a scab from an injury. Or it could be sun damage.
By far the best idea would be to take your dog to the vet, let them see it.
Hopefully it's nothing too serious, and heals soon.