i did create function as folllows

create or replace function get_value
(p_aid in number
,p_col_name in varchar2)
return varchar2 is
l_pa procurementaction%rowtype;
b varchar2(500);
begin
l_pa := ina_pkg.get_pa(p_aid);
execute immediate 'select l_pa.'||p_col_name||' from dual' into b;
return b;
end;

but when try to execute the function by following i get error

select get_value(19913,'awardnbr') from dual

ora-00904 lpa.awardnbr invalid identifier