我是你的小太阳我爱我的小太阳
[wŏ shì nĭ de xiăo tài yáng wŏ ài wŏ de xiăo tài yáng]
This nickname implies the user sees themselves as a source of warmth and energy for someone special, much like how the sun gives light and warmth to the earth. The phrase also conveys a positive and loving emotion.