How to get rid of rotten milk smell on my kitchen floor?

Pine-sol will take that smell away, Roopa.

You could try spraying a mixture of a little vinegar and some lemon juice where the milk was spilled. You may have to put up with the room smelling a bit like vinegar, but as long as you add more lemon juice than vinegar, it won't be too bad. After about a week, try washing (mopping) the floor as usual to remove any stickiness produced by the lemon juice/vinegar mixture.

What kind of floor do you have? If it is a wood floor the smell would surely stick. Never use vinegar, baking soda or other liquid content it will destroy your flooring. There are a lot of cleansing and odor eliminator in the market just ensure that you use cleanser that is recommended by your floor's manufacturer or appropriate for your floor.

I recommend you Lustro Italiano Cleaner and Polish which is specifically designed and PH balanced for Marble, Granite, and Dimensional Stone Surfaces. Compared to other polishes and cleaners, it creates a deeper longer lasting shine. you can find it in my source site.