Thanks for your reply.
I had a pneumonia infection 6 years ago, despite being vaccinated against pneumonia. It was caught early and treated successfully. There was a spot detected on the lung too., and I was a moderate smoker.

I gave up smoking and exercised moderately, and within 6 months to a year, the spot had disappeared.

Since then, in my annual CT scans, there have been smaller ground glass opacities that have appeared and disappeared.

I had gone for a long international trip ( 9 month ) outside the USA recently, after being fully vaccinated for Covid. I did have an unspecified infection overseas a year ago. I tried to stay masked and avoid crowds. Nevertheless, there were unavoidable trips to crowded hospitals to help family members.

One of my medicines was switched to Lisinopril on a trail basis a few weeks ago and I started coughing about then, which may be a co-incidence. It's the size of this opacity, and the coughing, which is making me nervous.

Thanks.