As has been said, tinitus can be caused by a few different things. It could be a simple thing like a wax build up or fluid build up. If you experience discomfort or pain then it may be an infection. The only way to find out is to see your GP. Do not be tempted to poke about with ear swabs, the golden rule is that one should not put anything inside the ear that is smaller than your own elbow.
I had the same thing happen to me before Christmas, I ignored it but on New Year’s Eve I started to feel nauseous and dizzy saw my GP and I’ve been off work for 5 weeks with labarynthitis so I would definately get yours checked out
Just adding my pennyworth - Tinnitus can happen more generally when a very loud sharp noise occurs near/adjacent to one's head and the resultant - permanent damage - will always be biased to the side next to the noise. Gunfire without protection is a major cause in the US but in my case - the sudden dropping of a lorry's rear loading platform onto the road surface as I was walking past started years of permanent discomfort. Some serious viral infections and side-effects of some medications are all responsible. In my very long association with Diabetes I have never heard it said (or proved) that Tinnitus is a symptom of Diabetes - but there - there's always a first time hahaha.
In my case, my tinnitus was caused by standing by a teacher fir ing a starting gun. I was 7 at the time, have had it for 55yrs. Not caused by diabetes.