getting a lighter in should prove no problem. they are legal, and many smokers carry them for when they are "craving" (read: hooked). the blunt will be easy. they aint gonna strip you... put it in a hidden pocket or tuck it in your sock if you have to.

if it is indoor, i doubt youll manage to smoke it. whos concert is it? usually if a concert expects weed, theyll be outside. so watch the people near you to see if theyre cool ,a nd make sure the smoke/smell aint gonna fill the area around ya