I’m not sure what nail polish really symbolizes or why she was painting from your knuckles down to your nails but nail polish is generally used to decorate or beautify.

Mother here could be your natural mother, spiritual mother or the Holy Spirit.

The colors purple and white stand out. The color purple represents royalty, authority, wealth, riches:
‭‭Luke 16:19 NKJV‬‬
[19] “There was a certain rich man who was clothed in purple and fine linen and fared sumptuously every day.

The color white represents purity,holiness,righteousness:
‭‭Revelation 3:4 NKJV‬‬
[4] You have a few names even in Sardis who have not defiled their garments; and they shall walk with Me in white, for they are worthy.

It could be that God is calling you to walk in holiness, righteousness, authority and wealth.

Hi.
Here’s some additional information about your dream.
Nail polish is for the nails only so the fact that it was being painted from the knuckles says that a larger area of the your life will be covered in this wealth and righteousness.

Please pray about this and ask God for more information.

Shalom!