In Western culture, which side of the nose that's pierced has to do largely with personal preference, while in traditional nose-piercing societies, such as India and Nepal, the left nostril is typically pierced. A symbol of social standing and marriage, piercing the left nostril is thought to ease child-birthing pain.
Piercing the left nostril is traced back to Ayurvedic medicine, which links the left side of the nose to a woman's reproductive organs. For Indian women, the nose ring is typically inserted before she is married and makes up part of her wedding jewelry.
Getting a nose ring pierced professionally is important to minimize the risk of infection as well as to ensure proper placement on the nose.