The old saying that a healthy dog has a cold nose is partly true. It's pretty normal that a dogs nose feels cooler than the rest of his body and is generally moist. However there are some times that a dog can have a dry nose and that's ok too. If you find discharge coming from your dogs nose, then something may not be right. A puss like discharge can indicate an infection. This can be a bacterial infection or he may just have something stuck in his nasal passage. It's not uncommon for dogs to inhale grass that can get stuck and cause an infection.
A bloody discharge from the nose could be a blunt trauma or may, in a worse case, be a sign of cancer. Dogs that sneeze often may get nosebleeds just like us humans.
In any case, it is strongly suggested that you see your vet. Don't clean the discharge as the vet will need to see it to determine what's wrong.