I also think that it's nothing to worry about--my two boys both have "freckles" in that same place, even though they are very light skinned and light-coated (golden retrievers).
That being said, can I be nosy and ask why you haven't chosen to neuter a NY city dog? Even if you're not worried about him becoming aggressive as an unfixed male, some other dogs you may pass in close proximity could possibly become aggressive merely at the scent of an unneutered male. As you know, the city is full of all types--human AND animal. This happened to us in Central Park when our Jack was less than a year old, and the attacker was a pit bull. Jack ended up with nearly 60 stitches, and my husband ended up with a broken arm after the dog turned its attack on him. Our vet was standing right there when the attack occurred and later he said that the only explanation he could think of was that it happened because Jack was not neutered but had the scent of an adult male dog--the other dog took this as a threat, as the pit bull was also not neutered. Needless to say, we did neuter our dog as soon as his facial stitches healed.
It's definitely something to consider--and I might also suggest checking with your vet to see if there are health reasons to neuter; opinons vary, but most vets I know recommend it as a prevention for certain cancers.