Thank you for your question, Alicia.  You need not worry about the grounds growing moldy.  That just means that a fungus is growing around them, which is the process by which nature breaks down the beans, so their nutrients can be used again by plant roots.  So, you're wasting a perfectly good (although moldy) resource!  You can also put them into an outdoor composting bin, where the fungi (and bacteria and several other microbes) help "recycle" them.  Here is a great Extension article on coffee grounds in the environment that might interest you:  https://www.gardenmyths.com/coffee-grounds-in-garden/#:~:text=The%20short%20answer%20is%20that,It%20is%20pure%20myth.

Good luck!