Hi Andy and welcome.  My tinnitus started rather like this 3½ yrs ago and
was very 'reactive' to certain noises; in my case computer fans and droning
sounds generally.

You tinnitus is not necessarily here to stay, but you should certainly visit
the doctor soon, and s/he can check whether this is a reaction to something
deeper.

Apart from that, remember tinnitus in itself cannot harm you and _usually_
is not caused by anything serious.  After your doctor has cleared you, try
refusing to think about it for a few days, then compare notes with yourself
later. A lot of tinnitus is in the brain, and if it's relatively mild and
the brain doesn't focus on it,  it can actually reduce.  There are various
techniques that can help this process along, but that's for later.

When I first had tinnitus, I was horrified and shocked. Three years later I
can assure you that one way or the other, most of the time I am not aware of
it and life is 100% as good as before I got it. So don't worry.

S