Hello Amit,
Please read SAP help, it clearly states when you convert a planned order to production order material components are copied from planned order to production order.
In your case it seems to me that you deleted the BOM after you had the planned order created, can you re read master data in your production order and check ?
Planned Order Conversion - Production Orders (PP-SFC) - SAP Library
Edit: Check an interesting note, 391846 - Modification: Postreading master data during planned order conversion. Post application of this you can automatically re explode BOM at planned order conversion.
Best Regards,
Ameya B.