getting constraint voilation

Question

-(NSString *)insertCigStatusIntoDatabase:(sqlite3 *)database{
    database1=database;
    if (insert_statement1 == nil) {
        const char *sql = "insert into SmokerCigInformation(nthDay) values(?)";
        if (sqlite3_prepare_v2(database1, sql, -1, &insert_statement1, NULL) != SQLITE_OK) {
            NSAssert1(0, @"Error: failed to prepare statement with message '%s'.", sqlite3_errmsg(database1));
        }
     sqlite3_bind_text(insert_statement1, 1, [nthDay UTF8String], -1, SQLITE_TRANSIENT);
       }
    int success = sqlite3_step(insert_statement1);
    NSLog(@"%d",success);

    sqlite3_reset(insert_statement1);
    if (success == SQLITE_DONE) {

     // return sqlite3_last_insert_rowid(database);
     return nthDay;
    }
    NSAssert1(0, @"Error: failed to insert into the database with message '%s'.", sqlite3_errmsg(database));
    return @"-1";
}