Q1). Can I rectify it by filing FORM GSTR-3B on July ???
Answer : YES. You can rectify ( reverse your ITC ) your mistake in your July month's FORM GSTR-3B.
Q2). If any amount of Interest is payable ???
Answer : YES. Since you have utilised the ITC to off-set your Output Tax Liability, Interest @ 24% p.a. under Section 50 of the CGST Act 2017 will be levied.
Mam , pls file drc03 with 24% pa interest. don't wait for 3B otherwise interest will be increased everyday. interest will be calculated from due date of Jan return to till the filing date.