That's a pretty serious fungal problem. Let the soil get as dry as possible between light waterings. Provide warm temps, good sunlight, and good air circulation to help deter the fungus.
The fungus is probably harmless to your plant. If you want to get rid of it, you will need to apply a systemic chemical fungicide as a soil drench. Cinnamon is not effective.
For future reference, always use soilless, peat-based potting mixes for your indoor plants.
