Unless you're seeing a lot of blood in your phlegm, it probably doesn't mean anything. On the other hand, blood where it doesn't belong can be a warning sign of a whole bunch of things, so you may want to call your doc or the office for some advice.

Well The CT scan has nothing to do with it.
I have had it happen to me several times. My Dr said if it is less than a teaspoon worth I probably tore a blood vessel in my lung from coughing too hard. But if it is a teaspoon or more in a day then to get to the ER right away.

When my lungs get inflamed then I have some bleeding. Emergency room if it’s a half a cup. Usually every allergy season I’ll bleed a few times a month for several months. If I have a bad infection, I will bleed.