As mentioned, it's tinnitus.
It is not abnormal, lots of people have it, but having it for more than a couple of days (generally after going to a gig or otherwise exposing yourself to loud noise) is relatively rare when you're young and can be a sign of underlying hearing loss so you should check with a doctor anyway.
Generally, tinnitus which lasts longer than that is permanent and doctors will not usually even be able to diagnose a source reliably so you're going to have to wait for your brain to adapt. You'll eventually learn to tune the sound out so you don't hear it but it can take a few months and it will always flare up from time to time. The key thing is not to focus on it or worry about it. If it's particularly annoying, try putting some quiet music on in the background to help you tune it out.
In the meantime, take care exposing yourself to loud noise. Assuming you've been routinely doing so (such as regular gigging or clubbing) this may actually be the cause of your tinnitus as you may have damaged your hearing. Get some unobtrusive ear plugs or don't stand right next to the speakers at gigs, because if you continue to make it worse it won't ever tune out. You may actually find you're more sensitive to loud noise anyway.
Even once it has died down, be careful. You only have one set of eardrums and making it worse will still bring it back.