How to make a bike seat hurt less?

In my cycling experience buying top of the line (expensive) seat/saddle will almost always solve's the problem. But i would not recommend that to you because you're just 12 and a beginner. For the mean time just adjust your seat to find the right height until the feeling of pain subsides. Perhaps the feeling of pain won't disappear immediately, you'll just have to keep adjusting the height during every long ride until you find that comfortable and painless feeling.