A black spot usually indicates a speck of dust on the sensor... it happens to all brands over time... and a white spot indicates a failed pixel.
With most brands you'll need to submit the camera to a factory authorized repair station. For Canon, for example, there are authorized repair centers in Honolulu and Hilo.
Or you could try the Rude & Crude (tm) method, hitting the camera hard against the heel of your hand repeatedly to try to dislodge the pesky little dust-speck fella from the sensor so it falls to the bottom of the camera body and hopefully stays there until you get back to civilization.
Probability of success is low for this this method, but the risk is also low and the cost is nil. I can report that I was successful in using this technique on a Canon G11 a couple of years ago, and since I never had another problem with it, I saved the money for a repair and banked it toward my next purchase.
Good luck.
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