Im sorry to say, what you have found is actually a partially eaten glazed scone
Kidding of course! That certainly looks like ambergris. There is a simple test you can do to verify if you think its necessary: What some people do is take a small needle, and heat the tip using a flame, and then carefully poking the end of the needle into the surface of your substance. Real ambergris, due to its waxy nature, will melt a little bit and will also release a small puff of aroma. If for instance you do the hot needle test, and the needle cannot penetrate the surface, then you probably have a rock.