What Is Wrong With My Right Lung?

Yesterday, out of nowhere, my right lung started bothering me. The pain is hard to describe, kind of a dull ache or a burning sensation. It's located on the right side, but high up in my chest and close to the sternum. I feel it when I take deep breaths, lie flat, or bend over. It's not excruciating, but more of an annoyance. I've experienced this before, but it went away on its own after a few days. I'm just wondering what the possible causes could be? I'm not even sure if it's lung related or cardiac? Could it be costochondritis?