Check your Dyntopo settings , try subdivide edges. you may need to add some geometry first, try adding geo with clay strips along the edge lightly , then smooth it out, you have a razor thin edge at the moment.
Looks to me like you have one or more axis locked in sculpt mode. They're easy to forget to turn off:
Also if you're trying to smooth out a rough area, increasing detail size is the better option. Decreasing detail size will add more geometry and preserve + reinforce the rough spots. The opposite will simplify and smooth out rough areas.