"Infant Sorrow" is one of Blake's Songs of Experience, a series of poems which contrast and complement the Songs of Innocence. Though I won't go into it in this answer - which, I might add, will be too short to do full justice to Blake's complex, concise poem - you really need to read its 'companion poem', Infant Joy, in Songs of Innocence.
The poem is written in tight little rhyming couplets, and lines of iambic tetrameter (though it's not always regular!):
My mother groaned, my father wept,
Into the dangerous world I leapt;
Helpless, naked, piping loud,
Like a fiend hid in a cloud.
The first stanza describes the birth being a "leaping" into a "dangerous world". The poem imagines the birth of the baby (who narrates the poem, we presume, in the first person) as a movement from safety into a dangerous world - and a world in which he is helpless, naked, and "piping loud". Does that mean crying - or singing? It's difficult to tell.
And, while the infant is born, Blake focusses our attention on his weeping father (why is he weeping - shouldn't he be happy?) and his "groaning" mother (is she experiencing a particularly painful birth?) rather than on the joy of the occasion.
Most scarily of all, the baby is described in a simile as like a devil ("a fiend") hid in a cloud. What does that mean? How might the baby be like a devil hidden under a (traditionally angelic!) cloud? Is birth a little demon breaking out into the world.
Struggling in my father's hands,
Striving against my swaddling bands,
Bound and weary, I thought best
To sulk upon my mother's breast.
The baby, in the second stanza, is struggling against the boundaries of the world: against his father's hands, against his 'swaddling bands' (the clothes used to wrap a new born baby in). The baby is restricted and "bound", and tired, and so he sulks on his mother's breast.
If the baby really is a "fiend", is he bound for good reason? Will something awful happen when he is unbound? Or is this a poem about the awful restrictions the world puts on people's freedom?
Questions, questions. Blake's poem is hugely ambiguous - and it 'means' a whole variety of things. Just remember, as you put together your own interpretation, to choose evidence from the text!