Hi Chiny! You should not have been able to get over to that door without the rain pencil, which I'm guessing you didn't have if you don't have the leaf pencil. In which case, this would be a bug and I'd need to know your device model and operating system, and how you made it over to that area so we can fix it so it doesn't happen to other players!
Unfortunately, I believe you will have to start a new game, as I'm not sure of a way you can get unstuck from there. My apologies!