Here are a few tips to help break in the right boot and reduce friction:

1. Use Thick Socks: It’s great that you wore boot socks. Continuing to use thick, cushioned socks can help reduce friction and add padding until the boot softens.
2. Apply a Leather Conditioner: Conditioning the leather can soften it, especially around the heel and ankle area. This can help the leather mold to the shape of your leg more comfortably.
3. Use a Boot Stretcher: Inserting a boot stretcher overnight can gently stretch the area around the ankle and heel. Many boot stretchers come with small plugs to target specific areas, which may help with that spot causing the blister.
4. Heat and Cool the Leather: Carefully warming the boot with a hair dryer for a few minutes, followed by wearing it until it cools, can help it shape to your leg. Be cautious not to overheat to avoid damaging the leather.
5. Bandage the Area: Until the boot is fully broken in, applying a blister-prevention bandage or using moleskin on the back of your leg can offer extra protection.