Which course to choose after 12th with Physics, Chemistry and Computer Science?

You can get admission in BSc Computer Science and B.Tech etc. in Computer stream other than (if not interested in) Bachelor in Chemistry or Physics etc.

Since you have not obtained BE related subjects in 11th/12th classes thus they would tell you as you are not eligible for Engineering as you are more related to Chemistry or Physics etc.

You can still pursue Computer related Bachelor or Master Degree in the future and become a Hardware or Software developer etc. Your focus on this would help you.

In addition, BSc Physics or Chemistry Degree also would help you to get a different job related to Health and Lab related department. And, additional Diploma in Computer would help in this field.

It is said that a person gets success in the area in which he has interest and liking. You are telling that you have interest in computer science. There are good opportunities in the computer science area and you can definitely go for B.Sc. in it.
Please note that computer science is an area which has developed manifold in the recent times and the advancement in IT technology are touching sky as new advancements are coming up in AI and Robotics areas. New software languages are being used by the experts due to their versatility and cloud based techniques are being adopted by many business houses for convenience and ease of business.
So it is imperative that you will have to work hard in this area and just having a pass degree in computer science will not be suffice for you to make a good career in it. You will have to acquire some skills parallel to your UG course which you can do through online learning mode and by the time you complete your UG course you would be well experienced in many new skills that you would be able to acquire in a parallel mode. It is obvious that you should score a high score in your UG so that chances are there for you to grab a campus recruitment. With additional skills like Python or Data Science or Digital Marketing and many more you can make a niche place for yourself in the industry.

Since you have not opted Mathematics in your class eleven and twelve, your chances for studying degree in Engineering is restricted since for admission in any engineering college is based upon the three subjects- Physics, Chemistry and Mathematics be it through competitive tests such as IIT or otherwise.
However, it does not mean that you cannot study computer science. You can have your option for B,Sc ( Computer Science) and for acquiring this degree, you will have different colleges conducting this course. All you need to qualify the eligibility criteria for this course.
There could be tremendous opportunity for your if you have really mastered in the different tools of computers including your familiarity with latest languages such as Pythons, Java, Ruby, Fortran, Pascal , Oracle etc. Apart from that you should acquire proficiency in Data Structure, Artificial Intelligence, Digital Marketing for which there are vast openings of jobs currently. It is not necessary that you should be well versed in all languages but your inclination for a particular language such as Oracle or Python will open your avenues. What is needed from your end is that you can impress the interview board with your command in your computer tools apart from showing your talents in the different skills such as your ways of representing of your capabilities in the different domains and at the same time you are having your eagerness to learn more the latest techniques related to your fields.
You will have the endless opportunities if you could master the tools of the latest trends including cloud computing so as to accelerate your path of progress. However. I would advise you to be a man of optimistic note apart from enough tolerance in the crucial hours at least before the eyes of the management so that you can achieve accelerated promotion in your working area.

As you have no mathematics subject in your 11th and 12th classes, you may not be eligible for B.Tech/ BE admission. But you need not worry. You have many better courses and even after completing those courses also you can get jobs in the IT field.
1. The best option is to go for BCA and then MCA. Once you complete your MCA, you will have equal chances as a BE/BTech candidate in the IT field. So after your 12th class, you can opt for BCA.
2. Go for a B.SC in computer science. Do some computer-related diplomas like Python, AI etc. and get into a job in the IT field.
3. Do B.Sc and then M.Sc in physics are chemistry and there are many jobs in these areas also. You can do diploma courses related field of IT and try for a job in that area again.