Wrong itc claimed in gst in 2017-18

reverse the itc as soon as possible in next month gstr_3b 

Different FY will not be any problem?

Do i need to pay interest on it?

Any interest paid earlier on excess claim of ITC will be refunded by crediting the amount to the recipient's Electronic Cash Ledger. In case of duplication of ITC claim, no refund will be allowed as it is a contravention of the GST provisions.