Urgent

Since this case relates to F.Y 2016-17, the law at that time was-

S.139(5) If any person, having furnished a return under sub-section (1) or sub-section (4), discovers any omission or any wrong statement therein, he may furnish a revised return at any time before the expiry of one year from the end of the relevant assessment year or before the completion of the assessment, whichever is earlier.

Therefore, you do have time till 31/03/2019 to revise the return.

Kindly note that later on, by Finance Act, 2017, the phrase "one year" was removed.

Position after Finance Act 2017,

139(5) If any person, having furnished a return under sub-section (1) or sub-section (4), discovers any omission or any wrong statement therein, he may furnish a revised return at any time before the end of the relevant assessment year or before the completion of the assessment, whichever is earlier.