Remove the stain with a damp, clean cloth. Massage it on the affected area until it is moistened, but without wetting it.
Apply a cleaning solution on a soft cloth. You can buy a special product, which is often found in specific kits. You can also prepare it at home by mixing a few drops of mild soap (such as detergent for washing dishes without
perfume or a shower gel for children) with distilled water.
Pass the soft cloth over the affected area until the stain is completely removed. Make movements following the grain of the leather. This will help you protect its integrity.
Use a dry, clean cloth to remove detergent residue or excess water. For now, don't worry about drying the bag.
Let it dry for about 30 minutes. Do not try to speed up the process with a hairdryer. If you are in a hurry, you could put the bag in front of a fan. Cold air is less harmful than warm air.
Once the bag is dry, apply a leather conditioner with a soft cloth. Massage it in circular movements. It will help keep the skin soft and elastic. Do not use a classic hand lotion, which can stain and deteriorate the leather.
You could polish the leather with a dry cloth. This will help you restore the texture and shine of the bag.