Hi, I've Had A Septoplasty And A Couple Of Associated

Hi,
I've had a septoplasty and a couple of associated procedures in 2013. however, I have been noticing sthat when I lay down , I could hear all this soft crackling, or small popping sounds behind my nose. It sounds like a bowl of rice crispies. Any idea what is causing the sound, and how it can be treated. It is interfering with my sellp and quite annoying.