The separator period at the end of any sentence is an implicit scope terminator that terminates the scope of any previous statement that is not yet terminated. When a statement is contained within another statement, the next phrase of the containing statement following the contained statement is an implicit scope terminator that ends the scope of the contained statement.
A conditional statement not terminated by its scope terminator cannot be contained within another statement.
Except for nesting conditional statements within IF statements, nested statements must be imperative statements, and must follow the rules for imperative statements. You should not nest conditional statements.