My ear started ringing after got shocked by loud sound 8 yesrs ago. Slowly getting worse and worse since then. Is it cureable?

Treatable. When dealing with tinnitus we don't talk about curing we talk about treating. The goal of all tinnitus treatment is to make the sound "neutral". The more your brain focuses on the sound the louder it will become. You need to see an ear dr. For a hearing test and evaluation.
Probably not. Tinnitus is a common symptom of hearing loss, which may be induced by sudden loud noise. It is important to be evaluated for this by an audiologist and/or ear, nose, and throat doctor, especially if the symptom is only on one side.