I used a colored leather balm to mitigate a similar problem with the seats on my 135i. I used a 600 grit sandpaper to remove the rough edges of the worn areas then wiped everything down with a rag with a little rubbing alcohol (gets rid of greases).
Once the leather is smooth and cleaned you can apply the leather balm, which comes in colors. That will hide the problem.
Here's where I got the color balm:
https://www.furnitureclinic.com/Leather_Recoloring_Balm