There are many skin disorders and disease that can cause a dog's nose to become scaled or crusty. The crust may become very thick, flake off leaving exposed pink areas, and even bleed a bit if the dog rubs at his nose and a piece falls off.
With this being said, let's first look at the most common reason for cracking or crusting:
Nasodigital Hyperkeratosis
Nasodigital Hyperkeratosis is the fancy, medical term for an idiopathic (which means that the cause is not known) condition that is manifests itself by the formulation of crust on the nose and/or paw pads.
This is not uncommon with brachycephalic breeds and therefore the Boxer breed is prone to this. This affects older, senior dogs most often, though dogs of any
age may develop this condition.
It should be noted that if you notice this type of issue on a young puppy that you are thinking of buying - the cause will most often be something more serious and it is recommended to refrain from purchase until you are able to obtain a legitimate clean bill of health from a reputable veterinarian.
The crusting on the nose may be light or thick, becomes worse without treatment and while crust may appear on any part of the nose such as around the nostrils, it most often will present as a thick crusting at the top ridge of the dog's nose.
Treatment
Since the cause is not known this cannot be treated with any sort of prescribed medication such as antibiotics or the like.
However, in many cases when there is NOT an underlying
health condition and the ONLY problem is unknown crusting, the proper nose balm will heal the Boxer's nose and restore it to its normal condition.