Is there no scope in theoretical physics?
I’m not sure what you mean by “no scope” It sounds like you’re saying “no future” or no good jobs. If your goal is to have a future and make a lot of money, there are a lot of paths which will require a great degree of luck. Barring luck, you should go for a profession that makes a reasonable wage regardless of your interest in it (doctor, lawyer, etc) and save money in an IRA or 401(k) until you are a millionaire. If your goal is to enjoy your life, then you need to think about what sort of life will make you happy and how to have that. As to work, it is either a tool to get you money (which guides you towards certain answers) or a tool to make you happy. If your goal in work is to enjoy it as it will be about 50% of your waking hours from now until old age, then pick whatever interests you most. Theoretical physics is cool as hell, and there is nothing a compsci person could study which is as exhilarating as fundamentally reshaping the way we as humans think about nature and reality.