Left nose aligns to Ida Naadi, the left subtle nerve that passes from the Ajna Chakram to Mooladharam representing the calm, cooling and healing energy of the Moon.

Right nose aligns to Pingala Naadi, the right subtle nerve passes from Ajna Chakram to Mooladharam representing the aggressive, fiery or strength giving energy of the Sun.

A girl before marriage is protected by three divine beings – Moon, Gandharva (Vishwavasu), and Fire. Before the Moon phase vanes, girls were given a nose ring on the left nostril to continue the effects of Soma or Moon to see her through puberty and fertile period as it eases the menstrual pain and protects the girl from sensing unwanted passions in the presence of men.

Later when she is protected by Fire and before she is given to her fourth protector, her husband, to ensure the continued effect of Fire on her, the right nose ring is given.

The nose rings those days resembled the Moon and Sun as worn by tamil women. if you look up the images of Mother M S Subbulakshmi, you can see the Besari (left nostril which resembles the rays from moon. Note the hole at the top, which represents the Moon) and the Mookuthi on her right nostril resembles the sharp rays of the sun.