Bonta imagines a small figure living inside his own mind, the "homunculus" of the title, and the speaker admits he wants to tame it. But the figure resists. He is a "left boy," which suggests something awkward or contrary, and also a "little Hercules," a pint-sized strongman. He is "the king of ham," so he seems to be a show-off who overacts and hogs the stage.
The speaker's account of himself is rueful. He keeps finding trouble and learning nothing from it. Yet the last lines turn the admission around. He is "a little / pleased at this nothing," and he calls it "my no that is no," a stubborn refusal that belongs to him. The mood is wry and self-teasing. The speaker seems half exasperated by his unruly inner self and half fond of it, and by the end he doesn't seem to want it fully tamed after all.