what they likely put is 'monsel's solution', which contains ferric sulfate, and acts as a hemostatic agent. the oncologist i was seeing also used it after my biopsies. i had minimal discharge the first couple of days, and days following, it got progressively heavier. it took a total of 9 days for it to clear, and on a day or two, when a large chuck passed, i actually had some bright red blood passing. i also called my doctor with the same concern. the physician assistant stated that if i was bleeding heavily, as in soaking a sanitary pad every 2-3 hours, then she would worry. but it was like a regular menstrual flow for me, and definitely more brown with coffee grounds than blood. it eventually passed, and i'm back to normal now.
i would continue to call your doctor if you are concerned.