Unfortunately, the door panel does need to come off. At least you can get the door open from the outside because if you couldn't, you would be in a pretty hard place right now. More then likely, the linkage just popped off the latch in the door.
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Once you get the panel off inspect where the latch release cable connects/clicks into the inside door handle. There's a small plastic holder that's probably broken and allowing the cable to get out of position.