brown specks in phlegm

so about a week ago i had a stuffy nose and a little bit of a cough. nothing too bad, however i did cough up a lot of mucus (gross i know) but then after my cough started to die down, at the times that i did cough up mucus, there would be little brown specks. i still have a little cough but my mucus has been normal. i’ve never seen that in my mucus before, thoughts?