Hello, I'm Dr Ralston. Thanks for your question.
It sounds like your dog might have nasal hyperkeratosis.
It tends to look kind of like this:
It is not known why this happens in dogs but it is characterized by an excessive amount of keratin that builds up on the end of the nose. Think of it like a callus on a person for example.
This tends to happen more commonly in older dogs. The tissue will usually build up on the tip, or dorsal portion of the nose as you have suggested. Sometimes, it might even crack or bleed.
For many dogs, treatment might not be necessary if it is mild. Or, a moist compress should be applied for about 5-10 minutes. This softens the excess keratin. Then another agent is applied to the area. Vaseline has been used as you suggested but there are many other agents which have also been used which might work better for your pet: petroleum jelly, A&D Ointment, Ichthammol ointment and salicylic acid/sodium/lactate/urea gel.
I have had good luck with a product called kerasolve. Here is a link to kerasolv Please click here for link to buy or see what the product looks like
It is important to note that you will not cure this problem. This is something that has to be nursed and maintained over time and treated as the event occurs.
For cracks and bleeding, a topical agent that contains antibiotic such as neosporine may be used.
Treatment should be done for at least 7-10 days until the signs respond, and repeated whenever flare ups occur.
If the lesions cover the entire nose, or the front of the nose, and there is pink damaged raw tissue, it is important to have the nose checked by a Veterinarian to rule out problems like lupus and pemphigus. They might look something more like this :
Notice the depigmented pink areas where black pigment has been lost. Crusty scabby areas and the pink depigmentation are hallmarks of this disease.
IF your pet looks more like that - you will need to have it checked by a Vet and a biopsy might be necessary. These medications can be controlled with a combination of drugs only available from your Vet.