Hello Aspirant.

The answer to your question is Yes , you can study computer science after completion of your B.Sc Physics Hons.

After completion of your current course you can take admission into any college providing B.tech a(Computer Science branch) you'll be directly starting from 2nd year instead of 1st.(This is because you've already pursued your B.Sc degree).

After completion of your B.tech you can go for M.tech if you want to continue with your computer science branch and make a career in it.

Best of luck !