The application can't be opened error

Hi. I've got this annoying problem, and I haven't been able to find a fix, believe me, I've been searching around for 2 hours now. I know I should not have done this, but I force quitted the app two times, and after the second time, everytime I try to open it it comes up with an error message: "The application "IDLE" can't be opened.", in this case the app I want to open is IDLE. I've tried doing the chmod thing in Terminal, but it just says "No such file or directory", and I tried the chmod with other apps too, didn't work either, said the same error "No such file or directory". I tried looking in the app's files, nothing that could help either. Then, I decided to post here. Do you guys have any ideas how to fix this? I have re-installed the app two times and restarted my computer two times too. It is not an app downloaded from the App Store.