Sand should be ok. Its been commonly thought that damaged barbels was generally caused by gravel especiallyif it has sharp edges. I think this has largely been debunked and the thought now is poor water conditions. Corys are prone to issues in high nitrate. I dont think that is the issue with you though.
I still think if the substrate has sharp edges it can cause issues, and that can include some sands i suppose.
I would just keep an eyes on things, maybe do a few extra water changes to ensure your water is good and clean.