For DIY solutions, keep in mind that you want to take care of your leather and that stretching boots should be a gradual ...

Use boot stretching spray on tight spots for quicker results ... consulting a cobbler for adjustments (they can help your boot stretch to a slightly larger size) or adding insoles for extra ...

like FootMatters Boot & Shoe Stretch Spray—which you can get on Amazon. If you prefer an in-person experience, you could also head to a local cobbler or shoe store to grab something similar.