For your specific camera, the other answers which state that the film you shot on is ruined and only the exposures you haven't shot can be used are correct. That camera winds film in the typical forward order: when loading a new roll of film, it winds the film on just a little to the first exposure, then pulls film out as you take photos, then rewinds it all back once it's finished.
On the other hand, some cameras, such as my Canon EOS 300, pre-wind the film and shoot in reverse order: once you load a new roll of film, it winds all of the film out to the last exposure, then as you shoot photos it will rewind those exposures one at a time back into the canister, and then once you shoot the last exposure it will just rewind that one back in along with the leader.
If you have a camera that winds film like that, then the answer is the opposite of the other answers here, which is that all of the photos you shot are safe (with the possible exception of the last one you shot if it isn't completely wound in), but any film you haven't shot on is now unusable. In this case, so long as you didn't wind any film out of the roll, those photos can still be developed and viewed. If you do accidentally open the film door, be sure to cut and discard the unused film on the takeup roll before removing the cartridge, and then immediately wind the remaining film in until you're ready to develop it.