It should be wise to know if what you got is a face-adhesive sticker or a face-adhesive static cling. These two are different and there are two different ways to handle for each of them.
To start, if it happens to be a static cling, you can easily take it off, soak it a bit with a water with soap, and then stick it back. The water evaporates by itself after a day or two. Static clings usually relax on the glass in days and the bubbles just disappear by then.
How about stickers? How should you handle them? Find out here.
