Mild, ongoing pain on the left side of the abdomen can be due to common causes like gas, constipation, muscle strain, or digestive issues, but it may also come from conditions like gastritis or kidney stones. If the pain is mild and comes and goes, try drinking plenty of water, eating light food, and avoiding spicy or oily meals. However, if it becomes severe, persistent, or is associated with fever, vomiting, or urinary problems, you should consult a doctor for proper evaluation.