Thumb injury

[GhostFighter]

I keep getting my thumb with my back hand and im not sure why this is. I have a small wraps inside and my technique is right so I think it must be something the way I feet my hand into the glove.
What is the main reason why the thumb would hurt when punching?

[SplitSecond]

either bad punching technique
loose fist
badly positioned thumb(some people believe it or not dont know where to tuck there thumbs when making a fist)

or your hands are badly wrapped with wraps too tight