No need to worry, google pasty butt and you will get a lot of threads and you tube videos even on how to care for chicks with pasty butt! Just wash it off and keep an eye on it! If it is really dry, sometimes you can break it apart with your fingernails, or just some warm water and a wash cloth. Most of them like the warm water. Just don't try to rubb off the umbilical cord that is a little under the vent. Good luck!
Oh yeah, I did use Olive oil on one baby where the little tiny feathers around the vent just wouldn't clean off, and they seemed like they were pulling, worked perfectly.