What should the scientist do if his hypothesis is not correct?

Reject it and think of a new one. A hypothesis is a temporary explanation for some observation. It is then tested and, if found to be incorrect, a new one has to be formed.

1st, he/she could do the experiment again,2nd he/she could check his/her procedure if it is reasonable,3rd, he/she can do it again and again and see if there is a pattern in results.