Because the problem started immediately after the lens hit the floor, and other lenses work normally on the camera, the fault is very likely inside this lens rather than the camera body. A scratching/rubbing sound during AF after an impact usually points to internal autofocus mechanism damage or misalignment. Manual focus still working does not rule that out.

This should be treated as a serious lens issue. It is very unlikely to be a practical DIY repair, since autofocus lenses have small internal parts that are difficult to realign or replace without proper tools and calibration.

The realistic choices are:

• stop using the lens if the noise is severe, to avoid making damage worse
• have a repair shop assess it
• compare the repair estimate with the cost of replacing the lens, since for some Nikon 35mm models replacement may be more cost-effective than repair

So: don’t attempt a home fix unless it’s something very basic like checking the mount for obvious external damage. Otherwise, get it evaluated and be prepared that replacement may make more sense than repair.