ORA-02287: sequence number not allowed here

create sequence tq84_seq;
create table    tq84_tab   (id integer, val varchar2(10));

begin
   insert into tq84_tab values (tq84_seq.nextval, 'abc');
   insert into tq84_tab values (tq84_seq.nextval, 'def');
   commit;
end;
/

select val from tq84_tab where id = tq84_seq.currval;

with seqval as (select tq84_seq.currval curid from dual)
select
   val
from
   tq84_seq       join
   seqval   on id = curid;