Thanks for your question on Healthcare Magic.
I can understand your concern.
This recent spot on chest
x ray was not present in your previous chest x ray (during college days).
So you should definitely concern about this.
So
consult pulmonologist and get done clinical examination of respiratory system and CT thorax.
CT is far superior than chest x ray to evaluate such spot.
If it is mass like lesion then
biopsy is needed to rule out cancer.
If it is infectious then
bronchoscopy is needed to identify the infection.
Don't worry about spread to others.
First diagnose yourself and then start appropriate treatment.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.