How to unlock Blocked Tables

Execute below query if you found any row kill that session .
select
c.object_name,
b.sid,
b.serial#,
b.machine
from
v$locked_object a ,
v$session b,
dba_objects c
where
b.sid = a.session_id
and
a.object_id = c.object_id
and object_name='MTL_SYSTEM_ITEMS_INTERFACE';

Output:-

OBJECT_NAME,               SID,SERIAL#,MACHINE
MTL_SYSTEM_ITEMS_INTERFACE,2948,7,our12-test.bilt.com

Solution:-
alter system kill session '7,2948 ' Immediate;