You've got to have the best wand.
The meaning is clear, but I'm baffled by the grammar.
First, I'm assuming 持た is a typo for 持った, but maybe not?
Second, I'm guessing that にゃいかん is a contraction of にはいかない. But the only grammar I know involving にはいかない is わけにはいかない and that would give the opposite meaning to my translation. I cannot find verb-past + にはいかない in any reference.
I know the character talks with a heavy dialect in the original book (Hagrid from Harry Potter) but I can normally see how what he says is connected to standard grammar. This one has me stumped.