Badly need help

[PO_0784]

My adult BP is starting to eat again! Well thats the good new :P. A month ago, ive noticed that one of his nostril was blocked by a white matter. But, he seemed to breath normally and nothing was going wrong so I tought I would just check him more and I put a humidificator in his room. Im starting to be nervous about it. What could it be. Here are a few details about the situation:

-He doesn't open his mouth to breath ( the blocked nostril doesn't seems to affect him much)
-He is eating
-He is acting normally...

I tried to clear his nostril with a Q tip and some water, it doesn't work and I dont know what to do beside of this. If you know any tricks , please tell me. What could it be, a retained shed piece ?

Thanks for the help !

PO