Yojijukugo came from China, so it’s no surprise that 針小棒大 features four on-yomi. The following phrase expresses the same idea but with wago:
針ほどのことを棒ほどに言う (hari hodo no koto o bō hodo ni iu: exaggeration) needle + pole + to say
The ほど (hodo) you see twice means “to the extent that.” So this literally means “to the extent that a thing is a needle, going so far as to call it a pole (is an exaggeration).”