Acceptable pain around iliac crest after using belt squat machine

[tomorrowtoday]

I enjoy squatting on the belt squat machine a lot because it takes my lower back out of the equation.
However, I always feel some little acceptable pain around the iliac crest the day after I do the belt squat machine.
The pain is really not serious and is more like a bruise. It’s only triggered when I touch the area near iliac crest.
I wonder if this pain happens to anyone. Is it normal to have this pain after doing the belt squat machine?
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[adviceplease]

@tomorrowtoday Yeah I used to get some irritation there when I belt squatted. Kind of inevitable unless the belt is really well padded