Never filed it return

Today i have filed itr 4s for 2013-14, 2014-15 but i have made a mistake i purchased the house during 2014-15 but in itr 4s column-B3 of year2013-14 i have selected house property income as "self occupied" but in 2013-14 i didnt have any house as i have purchased it in 2014-15 by mistake i selected self occupied option and submitted the return.....is it a minor mistake??? will there be any difficulty in future??

You mean to say financial year or assessment year. 

And definitely it's a mistake which needs to be rectified 

Kindly clarify whether its fy or ay

You need to file a rectification request u/s 154 as it is a belated return and return cannot be revised. 

@ anjali

Don't panic.

The house property purchased will not create any tax panelty as it is from savings from income earned before previous 3 years which are below tax limits.

So, just show as nil income (self occupied) in income from house property.