A cursor within another sqlserver cursor

I know I could do a join of tab1 with tab2, but that would not be the case, I need the two cursors.

When I run I get the error:

A cursor with the name 'cursor_tab2 ' already exists.

The cursor is already open.

I even understand the error, but I do not know how to solve it.

What is the right way to do this?

I have used it.

DECLARE cursor_tab1 CURSOR
    FOR SELECT id FROM tab1
    OPEN cursor_tab1
    FETCH NEXT FROM cursor_tab1
    INTO @idTab1

    WHILE @@FETCH_STATUS = 0
    BEGIN


        DECLARE cursor_tab2 CURSOR
        FOR SELECT id FROM tab2 where id_tab1 = @idTab1
        OPEN cursor_tab2
        FETCH NEXT FROM cursor_tab2
        INTO @idTab2

        WHILE @@FETCH_STATUS = 0
        BEGIN

            ...


        FETCH NEXT FROM cursor_tab2 INTO @idTab2;
        END



    FETCH NEXT FROM cursor_tab1 INTO @idTab1;
    END