Look at your alert file. If the tablespace is an permenant tablespace then the index creation space requirement is the issue at the tablespace where index is getting created. If the temp segment name is there in the alert then also the probable cause is the temp tablespace space issue due to index creation.

Increase both of them with auto extend and maxsize and see tomorrow with last ddl time whether any indexes created. Or simple ask your users if accessible, whether they received any errors. If you have helpdesk for your complany ask them whether any user errors are reported at the time the error occured.