Having the right saddle is important. Padded cycling shorts help, too. There are also commercially available products that help reduce chafing, such as Chamois Butt'r.
But when a sore crops up, the question is how to get rid of it. Most of us don't want to have to take time off the bike, after all, yet continued riding is liable to further irritate the sore. Hot, humid weather doesn't help.
There are numerous web sites regarding this subject, e.g. this one. My personal approach is to read all I can get my hands on, and see what works for me. Currently I'm trying a solution of tea tree oil (1 teaspoon of tea tree oil to 1 cup of water). In fact that's what I use for mildew on the shower curtain, but tea tree oil is supposed to be a good anti-bacterial; and if something is good for more than one use, so much the better!