Hi
This sounds like your door latch rod has come off which will cause the outside door handle to feel as though the latch has not disengaged.

The only way to fix this is to remove the inside door panel the check the latch has opened if not then you can open it manually from there once you have removed the door panel and the plastic skin that is under the door panel.

You will also find that the clip which holds the rod in place that I am talking about has proberbly broken.
If the latch and everything looks ok then spray some lubricant into the assembly area and then try to unlock it.

Hope this helps

Jason