Symbolism is when an author, or artist, uses a word, phrase, or other image to represent something deeper than the word or image itself.
In the poem "Infant Sorrow", Blake uses symbolism to depict the dangers a new born child must face. The symbolism of both mother wailing and father crying show the fear both possess in regards to the challenges they are to face in raising a child.
The image of the narrator struggling against his father and the swaddling clothes show the conflict and struggle one will face later in life.
After the initial struggle against his father, the speaker realizes the best thing is to give up and allow his mother to nourish him.