It is useless therefore to cultivate such tedious and unprofitable sciences which contain but false knowledge. It is but proper, O father, to engage in the cultivation of the knowledge of self. O father, the idea that ignorance is knowledge arises from ignorance only. A boy, O lord of Asuras, regards the fire-fly as fire.

In plain words: Prahlada says studying ways to beat enemies is tiring and useless, because it rests on false ideas. It is better to learn about one's own true self. Only ignorance mistakes ignorance for knowledge, just as a small child thinks a firefly is a real fire.