Hello Joanna, if you can post a photo and advise us too where the plant is situated/location growing.
At times, fungal growth at the soil level indicates too much moisture retention in the soil, as suggested by Anne earlier. At any point, you can try to scrape off a bit of the top of the soil and mix in some pumice or perlite. If you are in a cold area/winter area right now, I do not recommend repotting at this time of the year. Wait till mid or late Spring.
If you are growing your plant indoors, try to position it as near to a south facing window possible, and keep dry for now.
