Leather boots take a few weeks to break in. During this time, the boots might cause blisters and bruises, especially if they have thin or no padding. One way to reduce blisters and bruises is to ensure you buy the right size. If the shoe size runs small or large, it will likely cause blisters and feel very uncomfortable. Second, you can use leather conditioner or oil, which helps soften the boots without causing any damage. Apply the oil weekly until the boots are soft and then monthly to care for your boots.
Before the hike, you need to wear the shoes around the house with thick socks so make them soft. When you wear thick socks, you stretch the leather a bit, making it comfortable the next time you go hiking. If the boots still remain stiff even after wearing for a few weeks, consider using a boot stretcher to expand them for comfortable use. Avoid immersing your boots in water as this might make them shrink. Again, avoid exposing them to heat to break-in as heat will damage the leather.