Apple disease diagnosis (help!)

[Owl]

This is one end of one branch of an otherwise perfectly heathly-looking apple tree. I've recently acquired this garden so IDK the history. What is this disease and what should I do?
Sick bit https://www.flickr.com/photos/54992580@N06/7264259500/in/photostream/

Healthy bit
https://www.flickr.com/photos/54992580@N06/7264261294/in/photostream/

[JONA878]

It's almost certain that if you look back along that branch Owl, you will find a lesion. This is a canker.
Cut the shoot off a couple of buds back into good clean wood and it should be fine.
As it is on the end of a branch/shoot remove it and all should be ok.