Here is all the info you need: https://support.clickandgrow.com/hc/en-us/articles/360000947227-19-How-to-get-rid-of-mold-and-algae-
there is some mold indeed, but it is probably harmless.
But, I hope you don’t mind- to promote new growth I would suggest a different way to prune basil. Next time make the cut just above the previous pair of true leaves, this promotes new growth. If you make the cut too low or above cotyledons (first leaves) it will just die back and that also encourages mold to grow.
Here is a tutorial video on how to prune basil, I hope you find this helpful.