Simply growing your beard isn't enough. You have to take care of it.
If you don't, all your friends will have to deal with your smelly, flaky, prickly face (and so will you). The hair on your chin isn't the same as the hair on your face, so you'll need to wash your beard with a special shampoo and follow your regimen with a conditioner or beard oil. Over time, your beard will grow soft, shiny and smelling fresh.
And you can kiss your chin dandruff goodbye.