I am applying for next semester but I wanted to know whether I could send my CSS application early or not?
You can currently fill out a CSS Profile for Fall 2017 or Spring 2018. If that’s what you mean by “next semester” you should be able to submit it, as long as you have the supporting tax forms requested (2015 and 2016).
The CSS is not a scholarship application. It’s additional financial info that some colleges use to determine financial aid.
CSS Profile application for 2017-18 school year was available in October 2016. Maybe your school doesn’t require it yet, but you can certainly fill it out now.