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Take a simple paper painters mask and eye protection, and some dawn dishwashing liquid and water and wash it away. If you want, you can also go to the local hardware store and get some KILZ and paint over the spot that is now clean. This will help. You might also look outside and see what is out there.
Do you have mold out side on that spot? If so, you may have to do some renovating and see where it is in between. It might be something as simple as a small water leak from a window or drain pipes that are no longer working.
Mold is living, and will come back. You simply have to watch for it. However, if you feel unsafe, you can take a sample to a local lab and see if it's the kind you should be concerned about.
Concern runs the gambit between abject terror and ignorance of the problem.
Find your comfort zone and deal with it just as if it were mice or roaches. You sound like you caught it early. That is always good.
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