I've had tinnitus my whole life - or at least for as long as I can remember. Tinnitus in children is definitely underdiagnosed - for at least two reasons: 1) Children may not be aware something is wrong because it is "normal" to them - and 2) even if they do realize something is wrong, they may lack the language to describe what they experience. Possible causes for tinnitus in children is slight damage to hearing which may be due to low birth weight, high fever at some point in childhood, mumps, and some antibiotics. Very low birth weight or a virus acquired during pregnancy will usually lead to more severe hearing loss (which will not go underdiagnosed).
There is (some) evidence that using headsets where sound is (obviously) introduced directly into the ear canal all day long can lead to damage over time (even at low volume levels). This can/is a potential problem for people in call centres where there will often be background noise (leading to employees turning up their headset volume). Additionally, people with slight hearing loss will need to turn up the volume even further to compensate for their loss. If you use headsets daily in your job, I would recommend that a colleague checks your headset volume (to see if they find it too loud).
Tinnitus cannot affect your hearing, but it can affect your ability to hear.