Had Minor Lug Cancer Last Year...had A Lung Resection (not

Had minor lug cancer last year...had a lung resection (not large at all)..last CT a week ago found a few nodules small but...for awhile now when I cough up sputum, half the time there are specks of fresh blood and/or thin strands of blood in sputum. Hard to find a definitive answer if the lung nodules cause this or not. The specks are not "old blood" if that makes sense. What can cause blood? Thank you