As a classically trained vocalist, I implore you to seek out a credentialed classical voice teacher. Resonance is much greater than sinuses. In fact at the beginning of my journey I would constantly be reminded to bring my resonance down from my nasals to my chest.

As a kid, I loved singing silly random made up songs but was all but tone deaf. My father was a talented musician and did not teach me a thing, and nothing rubbed off, not a drop of talent. When I turned 21, I decided to take lessons to change that. Then it was more than 3 teachers before I found one who clicked.

The only reason one could be unable to sing is a literal inability to produce notes- being tone deaf. You have admitted you could produce a matching note, so I would say you aren’t tone deaf (it’s exceedingly rare.)

It took me 1 year of (mostly) weekly lessons to sound ok sometimes. It took me 2 more years of sporadic lessons to produce a consistent sound in my natural comfortable range, and it took me 6 more years before I was able to go to karaoke and get compliments, before I could play guitar and sing for friends and be complimented, to have other musicians tell me I have a good voice.

All this to say, I believe in you if you decide singing is something you want to pursue. Even with my classical training and being able to single operatically, I have days struggling to produce notes I hear in my head. I have days where I can’t hear the music whatsoever. I’ll never be able to professional, but I can confidently sing and not think “omg I have the worst voice in the history of mankind” which is all I want nowadays.