I fell 20 days ago. My index fingers are still numb. What can I do?

See your doc. Three weeks is long enough to see if it was going to heal on its' own. Time to see what the problem is. Maybe just a little median nerve irritation, hard to say without an exam.
Injury. You sustained some injury and should report this to your doctor so you can be examined to find the cause of the numbness. It has been 3 weeks and there must be a cause for the numbness.