Especially for a pup with white facial markings.
The white areas on a boxer are areas of no pigment. And pigment is something that develops over time - including after birth. In fact, it starts from a few specific points on the dog and spreads out from there (in utero, that is). Anyway, pigment distribution is not normally complete at birth - that's why the white markings on a young puppy normally "shrink" as the pup grows. Alongside that, the pigment round the nose leather and mouth generally take some time to fill in. Most of it is likely to be there by 8 weeks, but in some cases it can take a little longer. Even white boxers have black noses though
despite being pink in their early days of life.