Popping in one ear? i was listing to load music (not that loud) and now i hava a popping in my left ear? what is it?

Barometric pressure: If you've had a bit of a cold, or eustacian tube dysfunction, that can cause a "popping" in your ear. Also, if you are a swimmer, water retained in the ear canal can do that. If you are an aggressive q-tipper, wax can get pressed up against your eardrum and dry there, causing "krinkly" popping sounds.

Depends: Does the popping occur when you open or close (or both) your jaw? Has this happened before, trauma, etc. A thorough history and examination are needed, whether it is an ear problem, tmj/tmd or a combination of both.