Question

Nakul said I have made a terrible mistake yesterday change into indirect speech

Answer 1

Hey buddy
here's the answer

Nakul said that he had made a terrible mistake the day before

Answer 2

your answer

in indirect speech the sentence is as follows:-

$nakul \: said \: that \: he \: had \: made \: a \: terrible \: mistake \: the \: previous \: day$
here we have changed:-

have- had
yesterday-the previous day

hope helps