We're told Mia went under the knife a week ago, getting a Scarless Nose Rhinoplasty courtesy of celeb Bev Hills plastic surgeon Dr. Deepak Dugar.

The bandages have finally come off, and as you can see ... Mia's new nose is a lot smaller, and pretty darn cute. Nice work, doc!

Our sources say Mia's nose job is a long time coming ... we're told she's wanted one since she was 14, because her schnoz was one of her biggest insecurities. Yes, people who bare all for the camera can still be insecure.

Of course, Mia's signature look became her nose, eyebrows and glasses, so she was hesitant in recent years to make a change ... but she finally decided to go for it.

She wins this one by a nose.