Coughing up discharge and nasally noises

Hiya, My 1 year old pekingese keeps coughing up phlegm, hacking in general and making nasally noises like he has a blocked nose. He breathes perfectly fine normally, doesn’t have issues with breathing when running and is general pretty good with his breathing apart from this so I don’t think it’s BOAS or anything that severe. I noticed it just after he was neutered and my other boy hasnt caught it so it isn’t infectious. I’m asking on here mostly because I worry if I go to the vets they’ll just say it’s because of the breed and dismiss it. The closest brachy vets is 2 hours away so hoping for some advice or any idea of what it is?