Unbreakable Blocks

Whenever I Started Minecraft It Went Normal But Then Like 30 Minutes In I Went To An Island To Get Wood But When I Got There I Broke The Wood But I Couldn't Break The Wood So I Tried Breaking Sand (Didn't Work) So I Tried To Get On My Boat To Go Back (Didn't Work) Hopefully You Can Fix This Please And Thanks For Making Minecraft I Love This Game