The proposed translation is almost right. The main issue is that you should use the plural ablative—manibus meis—instead of manus meas for my hands (when following the preposition in implying a motionless location.) Hence:
In manibus meis[,] creatio
Is a right, word-by-word, translation. You can also play with word order and the elision of the verb without loss of meaning: creatio in manibus meis, in manibus meis creatio est, etc.
Update: As underscored by Joonas and Adam, the comma is not needed and might, in fact, make it sound less classical. Thinking it twice, I'd actually prefer the version without the comma, but I don't directly advise against it, since I think it adds a bit of readability for a less experienced, present-day eye, and you didn't specify that you wanted the translation to be classical.
Creatio works for both the Universe and a piece of art, but if you want to be more specific you may want to use other words: For example, mundum or mundum universum for the former, ars fabricandi for the latter (though I'm not sure how clumsy this sounds.)