With most cases of tinnitus it's not the noise that's the problem but your reaction to it. The more you panic, the more you'll notice it.
OP please largely ignore this because it is nonsense. While this can be somewhat true in some people and some people will benefit from psychological therapy as part of their treatment, it's dismissive and blame-casting to pose it this way. Tinnitus can be psychologically difficult, and affect work, relationships, leisure and sleep. It can worsen over time so it's good to get initial medical advice early. And rule out various serious medical causes. It's not the severity that matters, it is how it affects you and your life, based on lots of factors.
Treat it like a tantrumming toddler and soon it'll get bored and go and play nicely in the corner and you'll just hear the occasional grumble.
Also not always true. Some people need other help and early help can improve outcomes. There are specific sound therapies and specific technology to help with the condition. There are Tinnitus-specific support groups as well as 1-to-1 CBT to help you learn how best to cope. Severe tinnitus with or tinnitus as part of hearing loss, can in some cases lead on to further help at work, with equipment that links to your hearing aids or otherwise. Not everyone realises they have hearing loss when they do, not at first.
If the noise is just in one ear, speak to your GP.
No. Speak to your GP regardless. You will need an examination and a hearing test. Some presentations indicate very urgent or semi-urgent referrals. Lots of different things can cause tinnitus, some of them serious in their own right as well (not saying tinnitus isn't serious, for some people it can be life-changing). First, check out the NICE guidelines (just type "NICE and tinnitus" and "NICE hearing loss") so you can tell if you GP is following them and challenge if they are not. There's also lots of information via Tinnitus UK and RNID, they have helplines etc.