Once the shoe is even slightly soft in the heel there won't be a problem.
The issue persists however, if you get a blister from the hard heel and then continue to wear that same pair of shoes over the blister. It's double painful because the shoe is hard + it's rubbing against a sensitive blister.
The easy fix is to use a blow dryer on the heel of the shoe till the leather softens, and then bend the hard leather back and forth and break it in until it isn't as tough. You may need to do it a few times till it's fully broken in.
Then WAIT until the blister is totally gone before wearing this pair of shoes, otherwise the heel will still be rubbing on the exact spot where the blister is which might tickle.
