Return filled wrongly

I filled ITR-4 for the Ay 2014-15 claiming refund rs.8000. I am a LIC agent. I don't have any other income other than LIC commission. ITR processed and refund released. But in return I mistakenly chooses U/s94a column as 'Yes'. Now I received a notice from AO u/s 143-A. Is it going to be a problem. What should I do...plz help me.