Dear friend, welcome and thanks for entrusting your query here at HCM !
Good news is that your Xray report is absolutely normal.
A small amount of blood may come in sputum (mucus) if there is significant mucosal inflammation/ congestion that occurs with respiratory infections, colds etc.
Uncommonly such thing may happen with low platelet count
or clotting/ bleeding disorders.
sometimes Xray may look normal even though there are lung problems and your doctor can decide what among theses would have caused it.
I hope you are fully satisfied with the guidance I gave.
I would be glad to answer any further queries.
Thank you and Good luck !