If you suddenly developed it without any major accidents (like your eardrums burst from pressure) or continued harmful noises (construction is a big one). You should probably get it checked

Could be a symptom of an underlying issue and it might go away if you fix that

If you come back from that and it genuinely is tinnitus, then I recommend:

1. Keeping your mind distracted. Mostly easy if you are doing day to day stuff, hard when you're trying to sleep
2. Play ambient noises. I like ocean waves if I have problems with mine, it helps drown out the static
3. Exercise. Doesn't actually help reduce it, but it does help make your body ignore it IMO, and makes it easier to fall asleep.