Just because mold is black doesn’t mean that it is toxic mold. Commonly you hear people freak out about finding black mold. While, yes, the toxic strain of mold is black / greenish in color so are thousands of other mold strains which are not toxic.

In rare cases you could have a toxic mold problem which would give you right to terminate your lease if not taken care of. However, 99% of molds are not the toxic strain, so most likely you have common mold. Common mold can cause some irritation or allergies.