Crystals in the bottom of my booze - what could they be?

I have a bottle of strong peppermint schnapps in my room that I bought about a week or two ago. I noticed this morning that there are a few large clear crystals stuck to the bottom of the inside of the bottle. Is this just sugar or something? Should I be concerned? I don’t want to throw out ¾ of a bottle if it’s still perfectly fine…