Dell, may I suggest that you post this query in the template specific forum (template that you are using) and if possible please provide a url to the problem.
The member formerly known as Roland Deschain After your question is solved, please Edit your original post and choose the Solved message icon, thank you!
Linking to the index.php won't work, you have to link to a Menu Item.
Menus > Main Menu > Home
From here you can change the type, or relink the menu, but entering 'index.php' will just cause an error.
Normally this is a Frontpage Blog Layout.
In the more recent templates, RT hasn't used Frontpage Blog Layout, instead, the Home menus have been Article Layout Menu Items linked to a specific Article, usually Uncategorized.
If you just want to 'get back to normal', go back to the Home Menu and relink the Article.
Of course, if you are using a more recent template, you can change the Menu Item anything you like....