I just read this on a website:
"A discharge from the nose generally means trouble. Several diseases involve nasal discharge, including distemper, bacterial rhinitis, infected sinuses, and kennel cough (in puppies and toy breeds), so a trip to the veterinary clinic is definitely in order if Slugger' nose begins to run."
It also warns that the inside of the dogs nose can easily be damaged so don't try sticking anything up there. For more information:
http://www.canismajor.com/dog/nose.html