I think that it is a legitimate concern any time a rogue country like North Korea is launching anything like short ranged missiles. Even if it is just tests, it is still something that the international community should be aware of. I think that such testing should be met with harsh consequences.
The world should be concerned about North Korea's missile tests. Their autocratic leader is a mad man who feeds his relatives to dogs. If you will do that to relatives, what would you do to other countries? The North Korean regime seems to have no limits and is willing to do anything to maintain power.
North Korea is currently led by a leader just as crazy as his father before him. He represents a danger to the entire world. He plays with missiles while enforcing strict propaganda to force his poor starving citizens to worship him like a god. This is the type of personality that burns the world, we should all be very worried.
Short range missiles are the best North Korea has got. They do it every once in a while as a passive-aggressive demonstration of their strength, which they do not have, because they are financially and technologically underpowered and they even if they have nuclear technology, they are most likely not nuclear capable.
North Korea does a lot of grandstanding to keep its citizens in awe of it (which isn't overly difficult since they aren't allowed to see anywhere else) but it's all for show. Mutually assured destruction applies to and is respected by all nations, even ones as stupid as North Korea. They know if they attacked anybody they'd be wiped out by the end of the day.