If you have small brown spots on the lower part of your back, it is difficult to give a definite answer without seeing the lesion. It would be best to consult a pharmacist in person and show them the spot, or even upload a photo for their review. In most cases, if there are no symptoms, it is recommended to take a "wait and see" approach. Avoid touching or scratching the spot, wash it gently with soap, and refrain from rubbing it with a towel after a bath. Simply apply an unscented moisturizer 1 to 2 times a day. If you notice that it is temporary, there is no need to worry.