The ringing in your ear is known as Tinnitus. Tinnitus is a noise that is in your ears or head and no one else can hear it. You should visit your doctor and know the cause for your Tinnitus for it might be a cause of ear damage. In the mean time, try to distract yourself by listening to soft music.
It is referred to as tinnitus and is normally due to being exposed to loud noise such as being in close proximity to an explosion or extra loud music, I would suggest that you see your doctor right away as it can continue to get worse until you are completely deaf.