I personally have never heard that you cant close a tribal tattoo around your arm for reasons of bad luck, but that doesnt mean its not true to some people.
You are right, the inside of your arm is very tender when being tattooed. And yes, some people elect not to go any further and do not have a complete tattoo. In all honesty, that could be where that little "urban legend" came from...people were in too much pain to have their tattoo finished so they made something up so they wouldnt look so bad for not being able to handle the pain.
Its worth the guess.
