The vast majority of molds that develop on the top of soil or peat mix is saporotropic. Meaning it is a decomposer of organic material and usually harmless to the plants.
However, it's presence indicates that the air above the soil surface is too humid. Almost always happens if you sprout seeds in a tray with a dome on it. Which is something you shouldn't really do ever. Always sprout seeds with no dome in regular relative humidity of roughly 60-70% if possible. Lower is fine. Higher humidity will lead to molds and worst case for seedlings, damping off disease.
My recommendation, ditch the dome and keep them in a dry environment. I'd put them near my woodstove for the warm dry air if they were mine. You could also mist the surface with 3% peroxide to knock it back before you let it dry out a bit. But not too much as the peroxide can harm the seedling.