Vitamin D is usually not a reason for small height in the absence of features of rickets/osteomalacia.
The most common reason for small height is constitutional or familial.
There is still hope to gain some height if growth plates aren't fused.
Vitamin D supplements should be started with 2000 IU daily, at the earliest.
Next Steps
Consult a General Physician / Endocrinologist.
Health Tips
Avoid unproven methods of increasing height from social media, as it could delay the actual management.