'when blowing my nose/coughing things up I get brown chunks in phlegm?

Sinus. When having sinus troubles, wether a cold or allergies or sinusitis, it is normal to have secretions come out of your nose. These can be clear or colored fluid and can have solid particles too. You have to look at other issues to determine if need to see a doctor such as fever, blood, pain, shortness of breath, ...Etc.