If there is a spike on the right edge, it means part of your image is completely white and contains no data. Never let any substantial part of your image go completely white. Because it contains no data at all, it will always remain a white spot no matter what you try to do in post-processing. It’s better to keep the graph off the right edge. You only need to worry about this if the spike is right on the very edge of the histogram – if it spikes before the edge it is not a problem.