Hi there. Still going on? I'd take him into the vet. Believe it or not, this can indicate a problem with his teeth. They have long roots in their teeth and they can create symptoms like you describe if there is a problem. They also have sinuses like we do. So, one of the sinuses can be clogged or inflamed or infected. https://www.petmd.com/dog/conditions/respiratory/c_multi_rhinitis_and_sinusitis Get your pup checked out in case he needs antibiotics or a tooth pulled. Let me know how he is doing!