Given your description, here are few possibilities.
Nutritional deficiencies (
calcium,
vitamin D or
Vitamin B12)
Tinea Versicolor
Pityriasis Alba
Vitiligo
Post inflammatory hypopigmentation.
To determine the exact cause, it's best to consult a dermatologist online or you can visit the clinic so that we can examine the spot more closely and may recommend tests if necessary. If the spots are due to deficiency or other condition, early diagnosis can help in managing them effectively.