Question: In Tashahhud, what moment do you raise the finger? When you raise the finger, do you have to look at it?

Answer: One should raise the finger at the time when the word لا is said and put the finger down at the time of saying إلا اللہ .
يرفعها عند النفي و يضعها عند الإثبات (رد المحتار ٥٠٩ جلد ١)

You don’t have to look at your finger, However it is desirable to look down in Tashahhud-(at your lap)

و نظر المصلي………….و إلى حجره جالسا (نور الإيضاح ۷۲)