Given the many attributes of good health that you have described, your young age and the fact that these nodules are very small (by accepted criteria) and incidental findings, the likelihood of their being metastases is very low. I suspect that your doctor is concerned but, given the circumstances of your good health and the manner in which the nodules were discovered, I believe his/her not being worried to be appropriate.
My advice is that you and your doctor make a concerted effort to recover any and all X-rays (the films themselves and not just the reports) that you have had in the past to determine if these nodules might have been present in the distant past but so small as to not have been noted and/or reported. Were they found on any of the old X-rays that would definitely settle the issue in your favor.
Good luck
I have had acid indigestion for some time. Could it be stomach cancer? Is it common at 42?
Any advice/comments please?