I would be worried if some one call me and gave me the same news as you got.
Ok now lets dive in few thing that may show opacity,
1) an x-ray artifact
2) may be an old T.B patch that might have calcified and be seen as opacity in that X-RAY
3) calcium deposition due to some systemic disease
4) may be a cancer,
so looking at this above the chances of cancer is 1/4 Right ?
Its is very important to Take "CT SCAN" As radiologist
to see in detail what are dimensions of opacity .
So, Just be calm and go for the CT SCAN. This is an effort simply to release some anxiety
which is seen in Your case and that completely normal to think in fashion as only the CANCER Comes in mind of every day person as a first and foremost reason.