Depends on what you mean by a bruise. Does it hurt? How long does it last? Have you tried using the bathmate off center so the affected area isn't directly contacted? What does it look like?
In most cases it's nothing, but if there's pain or a serious bruise involved we'll have to figure out exactly what the problem is.
In most cases it's nothing, but if there's pain or a serious bruise involved we'll have to figure out exactly what the problem is.