Are you using bike shorts? If not, get two pair so you can always have a clean pair available. Cleanliness in the nether regions (both skin and clothes) is essential to prevent sores. If you've just started riding, your butt may need to toughen up. If you're still having problems after a couple months with bike shorts and good hygiene, consider a different saddle. A good shop will have loaner models you can try while deciding. Don't be cheap. The saddle is your most important contact point between you and the bike.