HOW TO REMOVE THE PART IN SOLID WORKS?

I hope this helps and is what you were looking for.

Answered with a tutorial: https://grabcad.com/tutorials/how-to-remove-the-part-in-solid-works

Stephen Nyberg is right - a much cleaner model. The remodel is better than my fix - but you did ask how to remove / fix your current model.

The easiest way to remove the "surface"; add a cut revolve based on a converted sketch (the one used to produce the protrusion).

Another way It can be done is with a cut revolve and delete body.

Answered with a tutorial: https://grabcad.com/tutorials/how-to-remove-the-part-in-solid-works--1

I can help you
you can just draw a sketch and make removal of material

Try this : Click under sketch > 3D sketch
Then click 'Convert Entities' and click the edges surrounding the area you want to remove. Once done, exit the sketch. Click 'Extruded cut' and select a plane almost parallel to the portion you want to remove. Enter a desired height and hit the checkmark. It should be gone. Let me know if it worked.

Well, I cannt open the file since this is a future version Solidworks so that I can try it but have you tried this:

Got to Command Line - Insert - Cut - Boundary (or "With surface")

Sir check it

The thickness is very less at a point