Hopefully they are correct in that it is just inflammation. For me, my sinus infections, always represent with inflammation. But my doctor can always just look up my nostrils and just tell it's an infection. I hope it is just as simple as inflammation/infection for you.

Maybe a second opinion would help. Do you have a general physician that you see for your general health and annual checkups? I found my general practice was very knowledgeable and made the best reference for me, the one that saved my life!

If you are confident and trust this ENT diagnosis then go for it and be satisfied, if not, get a second opinion.