Try wearing megathick socks in them around the house. I am v lucky to have a mother with the same size feet who hates wearing heels outdoors but apparently loves parading around her house in mine to wear them in for me.
A friend used to be a manager of an old fashioned show shop and found this was a common problem. He was taught to use the leather stretching machine kept in the back room for such occasions.He had some very satisfied customers
This wonderful machine was .................
the end of a sweeping brush handle . The nice rounded end that is
He held the brush tightly between his knees put the broom end against the part that was too tight and manipulated(think of buffing a toe cap) the shoe/boot until it seemed stretched enough.
The customer tried the footwear again in the shop and if it was still too tight he would 'put it through the machine' again.
Sometimes just for a laugh he would switch on the hoover while he was busy with the brush
saw something in mag the other wek. Get a car jack, wrap a towel around it and put it into the boot, turn the handle until its pushing agianst the boot, then over next few days keep turning slightly. HTH