Don’t worry, our St. Thomas has you covered:

Objection. It would seem that God cannot create anything, because, according to the Philosopher (Phys. i, text 34), the ancient philosophers considered it as a commonly received axiom that "nothing is made from nothing." But the power of God does not extend to the contraries of first principles; as, for instance, that God could make the whole to be less than its part, or that affirmation and negation are both true at the same time. Therefore God cannot make anything from nothing, or create.

On the contrary, It is said (Genesis 1:1): "In the beginning God created heaven and earth."

I answer that, Not only is it not impossible that anything should be created by God, but it is necessary to say that all things were created by God, as appears from what has been said (I:44:1. For when anyone makes one thing from another, this latter thing from which he makes is presupposed to his action, and is not produced by his action; thus the craftsman works from natural things, as wood or brass, which are caused not by the action of art, but by the action of nature. So also nature itself causes natural things as regards their form, but presupposes matter. If therefore God did only act from something presupposed, it would follow that the thing presupposed would not be caused by Him. Now it has been shown above (I:44:2), that nothing can be, unless it is from God, Who is the universal cause of all being. Hence it is necessary to say that God brings things into being from nothing.

Reply to Objection. Ancient philosophers, as is said above (I:44:2), considered only the emanation of particular effects from particular causes, which necessarily presuppose something in their action; whence came their common opinion that "nothing is made from nothing." But this has no place in the first emanation from the universal principle of things.