Don't say a word to your aunt. What she gave you is a lot more expensive than the cologne form of the fragrance. It's also much nicer than the cologne, is the truest form of the fragrance, and will remain truer and more long-lasting on your body.
You needn't give a second thought to the fact you're a guy. In Europe, perfume is much preferred over cologne by *both* men and women. Just remember that, unlike cologne, a little goes a long way with perfume. So, just put a very small amount on a couple of pulse points (carotid and wrist, for example). That's all you need.
I personally avoid cologne, much preferring the perfume version of a fragrance. Have you ever been in a place where you ended up with a smashing headache because someone was wearing "too much perfume"? Chances are good they were wearing *cologne*, not actual perfume. That's because cologne has more alcohol in it than perfume, and much of it evaporates into the air around the person, much to the distress of those in the vicinity. Perfume, by contrast, has more oil and clings better to a person. But remember, a little perfume goes a long way! It should never be spritzed all over the way cologne is. Enjoy your gift; it is far superior to the cologne version.