Try this, open your terminal then do;
sudo vi /Users/cthockey16/.ssh/known_hosts
Then arrow down to the line containing the pineapple's ip address, should be the second line. Type
dd
which should delete that line, then type
:wq!
which will write the new file and quit vi. If all else fails and you don't mind killing all your known hosts, just do a
rm /Users/cthockey16/.ssh/known_hosts
which will just delete the entire known_hosts file.