If the document was forged outside the Court and then filed in the Court, Section 340 of the Criminal Procedure Code is not attracted.
If the document was forged when it was under the custody of the Court, Section 340 is attracted and you can file a Criminal Miscellaneous Petition urging the Court to become a Complainant. You're barred to prosecute.
It's entirely up to the Court to, or not to, prosecute him and dismiss or allow your Criminal Miscellaneous Petition. Dismissal of the Crl. M. P. can, however, be appealed against in the Court above.