I did not see an option to file for stimulus check for my child who is born in 2020. do i have to wait for my tax return or IRS will automatically send it to me?

LOOK at the form 1040 in your return ... is the child listed at all ?   And if so which box is checked in column 4?

And which month  was the child born ? 

Yes. His name and ss# was listed there. He was born in October 2020.