Although I have long suffered from tinnitus, a sort of "passive" ringing in both ears (annoyingly at different frequencies), this year I've had the sudden onset of a new tinnitus only in my left ear which is much more "active" and insistent. It comes and goes, and seems to mainly be triggered by sound rather than masked by it. That is, I don't hear it when I'm going to bed at night, but I do when I'm sitting at my desk and listening to music or even just to the fans on my computer.
I have also gone to a doctor about it, went to have my ears cleaned only to find out that they're fine, and now I have a phone appointment with a specialist lined up in a couple weeks. The main thing to keep in mind is that, in all likelihood, it's nothing serious. Beyond that, there can be other triggers. Like you, I'm rarely in a noisy environment, especially over the last year. However, the last year for me has been extremely stressful, which can be a trigger for tinnitus. Keep in mind also that COVID-19 and the vaccines can have some impact on tinnitus [citation needed].
I think generally you're going to be encouraged to learn some mindfulness techniques in order to facilitate just living with it. In my case at least, I long ago learned to live with my usual tinnitus, so it generally doesn't bother me. This new one is a sonofabitch though so I might need some new tools for it....