In Jain Dharma, dahi (curd/yogurt) is generally not preferred, because it is a fermented food and is believed to involve mikrō-organisms / living beings, which increases himsa.

General Jain view:

• Strict Jain practice avoids dahi, especially if it is freshly set, sour, or fermented.
• Many Jains also avoid it at night and on upavās / partial fasting days.
• Some household practices may allow it in limited form, but the stricter and more traditional approach is to avoid it.

So, if you want the answer in a simple way: for a Jain following strict ahimsa, dahi is usually avoided.

If you want, I can also explain whether buttermilk, paneer, or lassi are allowed in Jainism.