You said the corset was from another person, as it, it belonged to her and she had used it? If that is the case, the corset was adapted to her body, not yours; so, when you put it on, it did not adapt to your curves, because it had already been adapted to hers.
That may be one of the reasons it hurt you. Never use a second hand corset for the reason I just told you: they are conformed already to another body, and won't fit yours.
Another one is that she laced it up too tightly. You should always lace up yourself, because only you can know how much is too much. If you do not know how to lace yourself, consider learning. There are plenty of tutorials in YouTube for this, and it's very easy.
No, no corset worn for 6 hours is going to cause permanent damage. Just do not use it anymore, and do not use corsets until the pain has gone away.
Corsets should NEVER hurt. If they do, any kind of corset, you are doing something wrong. Wearing a corset should feel like a hug, not like being squeezed by a giant hand.
And one more thing: if you are not used to being corseted, you should not wear a corset for periods over 2-3 hours, tops. If you have events that require corsets for long periods of time, consider fashion corsets, as those are more flexible. If you need to use steel boned corsets, break them in a couple of weeks before the event, just like you would with new shoes.