How do we write "My Love, My Muse" in Latin?

Rather than trust an anonymous person on the Internet, why not go to a university and ask a professor there? You could offer to tip them for their time.

Amica mea, musa mea?

Google translate helps offer some suggestions as well?

Since you are going to tattoo this… Please make 100% sure that you don’t f@ck up. Check with a latin expert?

Whenever you do a tattoo in a foreign language, make sure you do your homework. You will need to double check your translation with several sources. Nowadays Latin language is almost extinct and it would be really difficult to find a native speaker. Hence you will have to ensure that your translation is correct by either using a number of online translators or confirming it’s accuracy with a Latin scholar.

The simplest way would just be “meus amor, mea musa”. Which is just literally “my love, my muse” no other embellishments. In Latin, often adjectives follow the noun, but you can put them before the noun to show emphasis, which I think is appropriate in this case. All of these words are in the nominative case, “meus amor” being masculine singular nominative, and “mea musa” being feminine singular nominative.

I wasn’t sure about “amor”, but apparently this does work. Catullus would sometimes use “amores” (loves) to be a cutesy way of saying “lover”, like “darling” or “sweetheart” or something. But if you just want plain old “love” the concept, “meus amor” is the way to go.