Cleaning leather isn't hard. Basic cleaning methods are easy, can be done at home, and can prevent challenging stains.
Wipe the stain off with a clean, damp cloth. Keep rubbing the area until it is damp, but not soaked through.
Apply some cleaning solution to the soft cloth. You can use a store-bought leather bag cleaner, which often comes in a kit. You can also make your own by mixing a few drops of a mild soap.
Wipe the stained area again with the soft cloth until the stain is gone. Try to keep your stroking motions in line with the leather's grain.
Apply some leather moisturizer to the bag once it is dry. Use a soft cloth to apply the moisturizer. Rub the moisturizer on using circular motions. The moisturizer will help keep the leather soft and supple. Do not substitute regular hand lotion, which can stain and degrade leather.
Consider buffing the leather with a dry cloth. This will help restore the texture and shine to the bag.