Interior Design

Yes, you most definitely can pursue a course in B.Sc. (Interior designing) after completing a diploma in interior designing.

NID has a 4-year Bachelor of Design program wherein the first year is foundation while the following years are spent in specialising in a field of your choice (out of 8 disciplines), the syllabus thereby varies greatly. NID also offers a Master's degree programme in Design for a period of 2 years offering a range of other disciplines, each with a different syllabus.
The fee structure for both can be accessed via this link attached below: http://www.nid.edu/admissions/fees.html

The best course to pursue is Masters in interior designing from NID, Ahmedabad. That will not only give you the best education but will also lead to a high paying job and a better one than you are doing right now.

Your both choices of career are good. You must choose your career based on your interests to excel in professional life.

It depends on the course, it is INR 93000/-

Hi Andaz,
Some of the popular courses are:
B.A. (Hons) (Interior Architecture Design)
B.A. (Interior Architecture and Design)
B.A. (Interior Design)
Bachelor of Design in Interior Design
B.Sc. (Hons.) Interior Design
B.Sc. (Interior Design)
Bachelor of Interior Design (B.I.D.)
Bachelor of Science in Interior Design and Decoration - B.Sc (ID & D)
For top interior designing schools, please follow the link:
https://www.shiksha.com/articles/top-10-interior-design-schools-in-india-blogId-10599

If you are interested in the same course then this is the best course for you. A course without any interest will not lead you anywhere so, stay in the same field and work hard. Don't worry about the job, if you are good at your skills you will definitely get a good job.

Thye best colleges for Masters in interior design is NID and NIFT.

The fee structure for both the courses differs from institute to institute. Refer to the links below :
Fashion Designing: https://goo.gl/5PaGPY
Interior Designing : https://goo.gl/AxNHco