Its small…might want to check the right one too[/quote]
Seriously, take the comment about Arnold and quickly google a shot of him hitting a front double bicep pose. You will easily see one side that has a nice long muscle belly, while the other side displays a higher peak, yet definitely shorter looking muscle. Of course when your arms are around 20" a piece, no one nit picks.
Genetics determine your muscle shapes, and if yours are a little different, don’t sweat it. If one is smaller due to the other being naturally dominant, it may catch up, it may not, but I promise that no one else will notice, nor even care.
You’ve got too much work to do if you honestly want to build some muscle to be worrying about such a silly little thing.