In reference to your query, in case the HSN details have been missed out in any GSTR 1, please just ensure to rectify the same in the next to be filed GSTR 1.
There is no specific prescribed penalty for this error, therefore if at all any penalty is levied, the chances of which are negligible, it would be as per general GST provisions.
Please connect in case of any further clarifications.
Thanks & Regards,
CA Aditya Dhanuka.