I usually use Lexol PH wipes for things like this. Lexol makes a cleaner and a conditioner, and usually I only use the conditioner for removing things like denim transfer, etc. - but for a real stain, I'd try the cleaner. Unfortunately since water is not taking it off, it's something that is stuck on or soaked in. The leather care threads are pretty detailed.
Do not, do not, do not use baby wipes (insert praying hands emoji lol).
TL;DR....you could try a tiny dab of a simple leather conditioner first. Patch test on the bottom of the bag. Good luck.