Nipple shadows are apparent in 10% of chest x-rays. The shadow is caused by the fact that the nipple normally protrudes outwardly from the surrounding tissue and upon contacting a flat surface, an arch shaped air space is created which looks like a shadow on the film. When a lateral film is taken, the anomaly is not seen which suggests that it is simply a shadow not any thing more than that. Therefore what the x-ray technician told you is correct. As long as a radiologist looked at the x-rays with and without nipple markers, as well as with a lateral film, then you have nothing to worry about.
Most x-ray films are done as PA and lateral. A PA film is done by you standing facing into the x-ray film such as the x-ray are shot from behind you. A lateral film is done by you standing at a 90 degree angle to the x-ray film and the x-rays are shot at you from the side. Finally nipple shadows do not always have to show up on an x-ray, they only show up 10% of the time. If they did not do a lateral x-ray it may be a good idea to ask your doctor if to do it just so that it will give the both of you some peace of mind.
To answer your question, yes I do believe in God. What I do not believe in is people who claim to have special powers and make claims that can not be proven or disproven (may be that's the skeptic/scientist in me). The only thing that I'm willing to take on faith is that God exists and I'm willing to accept that without any proof. In terms of the x-ray, I really do not think you have anything to worry about. Usually doctors cannot tell by just listening to someone's lungs if they have cancer. This is the reason why we have so many radiological imaging techniques. In terms of blood work, this can be helpful in diagnosing cancer when doctors look for specific markers such as CEA, Parathyroid Hormone, cytokeratin fragment 19, etc. However blood work alone does not help diagnose cancer. Diagnosing cancer requires a combination of physical exam, blood work and radiological exams. Each test works to confirm a diagnosis. Even radiological images are not sufficient on their own as sometimes seeing is not always believing as evidenced by your experience with the nipple shadows.
Yes you will most definitely be in my prayers. I'm sure that things will turn out the best for you. Just keep your faith in God. What doctors can't fix, God can!
As I said I don't think you need to worry. Your description sounds very much like a nipple shadow.