Wow SilentSiren49 that’s quite some pressure there!
And now for the questions:
> How long have you been doing hot yoga and how frequently?
> Can you describe the position that you achieve in this pose?
> And do you get a sense of when during the pose you feel the most pressure on your feet?
> Are you sitting upright or part/all the way down?
> If you are going back, do your knees stay on the ground?
> Perhaps you are very inflexible in that area and/or the circulation to your feet is needing some re-invigoration.
I have not had anyone report bruises (they don’t tell me everything 
) but one can sure feel the effects of a thin mat, or rough carpet, or hard floor, or a thin mat on a hard/rough floor or other combinations including when and how it happens in your body (see above)!
It could be simply that, or it could be something you need to check out if for example you find there are other signs, say easy bruising for other reasons in other body locations.
I will look out for your response!
Namaste
Gabrielle 
