First off, get a pair of cycling shorts. They make a really big difference. If you don't like wearing bike shorts because of how, uh, revealing they are...there are also short "liners" with padding
like these or you can get baggy shorts with built-in liners
like these.
Also, make sure your bike fits you correctly. If the seat is too high it will put extra pressure in weird areas. Also, the saddle should be pretty close to level from front to back...if you have the nose of the saddle angled up too much you'll squish your doodads. This is not good. A decent bike shop should be able to help you out with bike fit...usually for free or a few buck for a quick fitting.
Lastly if you're having issues with chafing and not bruising (although it didn't read like you were), a few well-placed dabs of vaseline or similar before donning your shorts will help a lot with this.
Whatever you do, you will have a somewhat bruised-feeling booty for the first few rides. Keep the rides short and bump up the distance as your butt toughens up. It is somewhat like the weight-lifting analogy as unused muscles will be sore after your first few workouts.
Fausto