Find out how you can turn your bath hot water down to 50'C - it can dramatically reduce the severity of a scald. Create a 'child-safe' play area to restrict access to dangerous areas. Your pre-schooler is now increasingly active, impulsive and even more adventurous. They may be able to scale a pool fence with assistance from garden furniture, or a large pot plant placed nearby. This is the age group when injuries start to occur from playground equipment and trampolines in the backyard.
Dog bites are also common, sometimes even from the family dog.
Keep large objects away from the pool fence so that your child cannot climb it. Supervise children around dogs. Even the tamest dog can have a wild moment. Consider buying a dog only when your child understands how to behave around them, then choose a breed that is suitable for children. Regularly check all play equipment to make sure it doesn't have any broken or worn parts.