you have to delete the new datafile as well however this will force you to drop the tablespace afterwards, since it seems that that tablespace is holding index segments so there is not much harm dropping the tablespace since indexes are relatively easy to rebuild

in NOARCHIVELOG

1. startup mount
2. alter database datafile '/u02/oradata/index00100.dbf' offline drop
3. alter database open
4. drop tablespace INDEX001
5. recreate the tablespace
6. recreate your indexes