Error(10,4): PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following: end not pragma final

create or replace TRIGGER "VALIDATE_DOA_DOD" BEFORE UPDATE ON IN_PATIENT 
FOR EACH ROW
BEGIN
  IF :NEW.DOD < :OLD.DOA THEN


    enter code here


 RAISE EX_INVALID_DOD;
  END IF;

  EXCEPTIION
    WHEN EX_INVALID_DOD THEN
      dbms_output.put_line('Date Of Discharge must be greater or equal to Date of Admition');

END;

1. replace the 'enter code here' with something meaningful, or remove it
2. edit EXCEPTIION into EXCEPTION
3. declare your exception EX_INVALID_DOD

So:

create or replace TRIGGER "VALIDATE_DOA_DOD" BEFORE UPDATE ON IN_PATIENT 
FOR EACH ROW
declare
    EX_INVALID_DOD exception;
BEGIN
  IF :NEW.DOD < :OLD.DOA THEN


     --enter code here


     RAISE EX_INVALID_DOD;
  END IF;

  EXCEPTION
    WHEN EX_INVALID_DOD THEN
      dbms_output.put_line('Date Of Discharge must be greater or equal to Date of Admition');

END;