Reject credit note gstr2

hi,

While checking gstr 2A for march 2017-18 i came across a credit note entry , but i haven't received any such credit note from that dealer . I called him and he confirmed it to be a mistake by his accountant but he has already submitted gstr1 for same.
I could not reject that credit note as editing for gstr2 is not possible.

if i don't reject that credit note it will make a difference in my gstr3b itc declaration and gstr2 itc calculation for FY 17-18

please help with this