Will show you what your full current path is. Then, you can retype the whole thing without the parts you don't want, like this;
If you want to get fancy and automatic, you can use the sed program to remove the last entry automagically.
export PATH=`echo $PATH | sed 's/:[^:]*$//'`
Just copy and paste that to a terminal.
Remember, everything you export is forgotten when you log out anyway, unless you put the command in your ~/.bashrc file.