Macos – OS X Terminal ends session at opening : permission denied

I have an issue with Terminal on MacOS X 10.7.4. I know where it comes from, but I don't know how to solve it :

Yesterday, I installed fish-shell as a shell replacement. Following the installation instructions, I ended typing the following command :

chsh -s /usr/local/bin/fish

I noticed I had to do a :

sudo bash

for it to work.
Once done, I quit.

Today, I try to run Terminal and I see te following message :

Last login: Wed Jun 27 12:38:01 on ttys000
login: /usr/local/bin/fish: Permission denied

[Opération terminée]

(yes, I'm French, which explains my poor English). I cannot type any command since I have no access to the Terminal.
I tried with iTerm2 but same issue.

No command is set at launch in the default profile of Terminal/iTerm2 (well, in the UI).

How can I take the power back ?

Thank you.