You found the perfect pair of boots, but they're a tad too small. Or, maybe one foot is bigger than the other and shoes right out of the box never fit you correctly. There are several methods you can try to stretch your leather boots without taking them to a shoe repair shop.
Rub the inside and outside of the boot with leather conditioner from a boot or shoe store. After the boot dries, wear it as usual and walk around as much as possible. Repeat the process as many times as necessary to In order to get a comfortable fit. This method works best for a shoe that needs to be stretched less than one size.
Spray the boot with a shoe stretching liquid or spray. This product can be found at a boot or shoe supplier. Apply a generous amount of the stretching solution to the boots, concentrating on the area you wish to stretch. While the boots are still wet, put on one or two pairs of thick socks. This will add bulk to your feet. Use one pair if you need to stretch a small amount, and use two pairs or more if you need to stretch the boots substantially. Put the boots on over the socks and wear them for several hours, walking around as much as you can.
Spray the boots with shoe stretching liquid and insert a wooden or metal shoe stretcher inside the boot. Adjust the tension to the stretcher so that it fits snugly inside the boot, and let the stretcher remain inside for one to two days. This method works best for a boot that needs to be stretched a full size or more. After removing the stretcher, test to see whether the boot fits better. If it is still too tight, reapply the stretching liquid and put the shoe stretcher back inside for another day or so.
Remember that although it is possible to stretch a shoe, it is not possible to "un-stretch" a shoe. Don't try to stretch the boots all at once. Depending on the condition and flexibility of the leather, it may only be possible to stretch the boot one to two sizes larger.
Some shoe stretching liquids and sprays may cause the dye on the boots to fade or run. If you're concerned about the colour changing, test the spray on a small area first.