File a divorce petition on ground of adultery and seek custody of your child.

File a criminal complaint against that man u/s 497 of IPC and file a child custody case before district court of area where the child is residing for custody of child under Guardian and Wards Act.

if she is not interested in living wiith you then go for divorce on mutual grounds and decide about the custody of child

You have abundant legal remedies.

1. Firstly you may prosecute your wife's paramour for adultery and bigamy.

2. You may seek divorce on the ground of your wife's infidelity.

3. Lats but not least, you may file a case for child custody to get your child. If you want your child back then act swiftly lest delay in bringing the legal action ousts your rights.