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I've lifted the car like that with a floor jack on the body seam at the jack point without issue, but I would never get under a car without putting it on a jack stand first. It is very convenient to lift the car this way to change brake pads at the track.
Hopefully nothing serious. There's not a lot you can do to fix them without welding on some small nuts and slide hammering them out. Worst case (very, very unlikely) you can bend the chassis. You'd have to drop it pretty hard on the stands to do that though.