There are few possible reason of this error:
- permission and ownership on tables files in /var/lib/mysql is not correct, ideal ownership should be to mysql user and permission 660.
- table not exist, check with show tables.
- table created in uppercase, set lower_case_table_names as per your application requirement.
- table is corrupt, repair the table.
if all above points are ok then use
--skip-lock-tables parameter with mysqldump.
I am sure this will resolve the error.