I'm reposting here the default value of $PATH env variable, in case you screwed up your $PATH.
Just execute, export PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin
But ideally, remember to do this before you change your PATH variable.
1. In CL, echo $PATH
2. copy the result in file that is already open
3. change your $PATH.
4. If something is wrong, in CL execute "export PATH=savedvalue"