After just a few miles of cycling, my bottom gets sore. There is no doubt bicycle seats can be irritating. Friction builds up quickly, particularly in hot weather. Yet the indignity can mostly be avoided by, shall we say, getting to the bottom of the problem. Most important, adjust your seat correctly.
Most people ride with their seats too low and tilted up too high in front.
This is hard on the knees as well as the butt. Most local bike shop operators will make these adjustments for a few dollars. Also, avoid riding in jeans, shorts or other pants that have heavy crotch seams. These seams can grate against the skin and in no time leave their mark. As an alternative, try cycling shorts.