I am sure your answer to this question would be "Yes". Because most of the astrologers suggest yellow sapphire to be worn on the index finger.
Let me ask you two questions now:
1) At the time of havan while offering havan samagri in auspicious fire do you use index finger ?
2) While reciting mantra with the help of a japa mala(rosary), do you allow your index finger to even touch the mala ?
The answer to both the above questions is certainly a "No".
It clearly shows that the index finger is considered very inauspicious for all auspicious activities. That is why this finger should not be used for wearing any gemstone, not even yellow sapphire. Yellow sapphire gives better results in ring finger. This has been testified by renowned astrologers L R Chawdhri and Sanjay Rath as well.
If you are still wearing the ring on your index finger, you can change the finger and put it in ring finger of right hand on a shukla paksha Thursday after following the proper procedure of mantra recitation.