It is not your fault nor should you be blamed. We do understand that you truly love and care for the dog. It doesn't make you a bad person by having to give up your dog. Border Collies are simply not for everyone. Fortunately, there are ways of dealing with the behavior.
Education is the first step.
Learn as much about Border Collies, their herding instinct, etc. as possible. Attend a trial or two and see these dogs at work. The second thing to do is to work on obedience. A well-behaved dog can be controlled when in these situations but they must be worked with extensively. Lastly, talk to a local rescuer, Border Collie expert, or behavior intervention specialist to help you deal with the nipping.