About a week ago, I had a very scratchy red throat that became inflamed and I had a hard time swallowing however other than that I felt fine.  Two days later I actually felt sick with more symptoms of congestion, pain behind eyes, cough, sneezing and low grade fever. I followed up with my family doctor yesterday and she gave me antibiotics for a sinus infection.  Today I noticed black streaks in my nasal discharge. Not much, but it was there and I've seen it before but just ignored it the last time I saw it.  I'm usually pretty healthy but I do have chronic sinusitis and two years ago I was in the hospital with pleurisy due to breathing in mold in my office at work.  

What are the black streaks? Should I notify my doctor or is it nothing to worry about?   Thanks!