Hello there,
There are many good courses after you have completed your Class 12. Some of them are as follows:

1. Under medicine, you have these courses:
Bachelor of Medicine and Bachelor of Surgery (MBBS)
Bachelor of Dental Surgery
Bachelor of Pharmacy
Bachelor of Medical Lab Technology
Veterinary Science & Animal Husbandry (BVSc. AH)
Physiotherapy (BPT) or Occupational Therapy (BOT)
B.Tech/BE in Biotechnology
B.Sc. in Agriculture and Environment Science
B.Sc. Home Science/Forensic Science

If you have a bio-math combination, you can choose B.Tech courses on the following biology related subjects:
Biotechnology
Biomedical engineering
Healthcare data mining
Cognitive neuroscience and artificial intelligence
Nanotechnology
Robotics

2. Under Engineering, you have these courses:
Computer Science Engineering
Electrical Engineering
Mechanical Engineering
Aerospace Engineering
Chemical Engineering
Civil Engineering, and so on.

These are the two broad groups into which science is divided after 12th standard, Medical and Engineering. You can choose any course from above. Also if you want you can go for Business subjects or Humanity subjects. It entirely depends on you what you will choose. Remember, you can only do great in a subject if you have full interest in that subject and truly like the work you are doing.

Hope this information helps you.
Good luck!!