Put on your skates and note where you feel tightness. You could feel tightness in the width of the skates or in the length.
Trying loosening the laces on your skates. This might give your foot more width if needed. If you usually skate with socks on the feet, try skating barefoot to make the skates looser all around.
There is no proven way to stretch skates on your own, so the only option you have is to bring your skates to skate shop to make sure you keep the integrity of your skates. Skate shops have boot stretching machines that can lengthen and widen your skates.
There is also shoe-stretching liquid you can buy. One brand that is safe for hockey skates is Elite Liquid Shoe Stretch. The liquid can stretch the upper material of your skates and help smooth out any area of pinching. Spray the liquid on the upper parts of the skates and areas where pinching occurs. Put your foot into your skates to stretch out the skate.
If after boot stretching or using shoe stretching liquid your skates are too tight, consider buying a bigger size.