Hlo Kamlesh.,you have to pay the amount 1040 along with interest. If the ITC is taken from exempt supplies/ supplied used for personal use, it is to be shown in 4(B)(1) and if it is for others, shown in 4(B)(2) in GSTR 3B. You can calculate interest at 18% p.a as it is not willfull mistake. Otherwise interest will be 24%p.a.