WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

Yesterday I setup my node for the first time. After battling an rvm installation for the better part of a day I decided to wipe my node clean and start over. So I blew the image away and started over. When I try to ssh I'm getting the following message. I know there are instructions in the error message, but I'm having trouble following them to a solution. Can someone help me?

Thanks

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
xx:xx:xx:xx:xx:xx:fc:c7:a9:0f:e2:7a:a2:5e:e1.
Please contact your system administrator.
Add correct host key in /Users/bopritchard/.ssh/known_hosts to get rid of this message.
Offending RSA key in /Users/bopritchard/.ssh/known_hosts:21
RSA host key for xxx.xx.xx.xx has changed and you have requested strict checking.
Host key verification failed.