Sec138 ni compromise related

Yes,he can do so by filing an application u/s 257 crpc.

file application under section 257 of Cr P C .

Please read Section 257. Withdrawal of complaint.
If a complainant, at any time before a final order is passed in any case under this Chapter, satisfies the Magistrate that there are sufficient grounds for permitting him to withdraw his complaint against the accused, or if there be more than one accused, against all or any of them, the Magistrate may permit him to withdraw the same, and shall thereupon acquit the accused against whom the complaint is so withdrawn.

Yes the complainant can withdraw the complaint at any stage owing to the compromise or out of court settlement, he can be permitted to do so by filing a petition under section 257 cr.p.c.