If you want to leave the BCOM course then I would recommend you to cancel your admission from the college you are studying BCOM and then you have to take admission as a fresher with the help of your 10+2 result, in the BSc course at the college of your choice. So if you wish to go for the BSc then you can obviously go for it cancelling the admission in the BCOM course.

The top BSc subjects you can opt for the best career ahead after PCB in 10+2:

• Zoology
• Botony
• Forensic
• Forestry
• Biology
• Biotechnology
• Bioinformatics
• Food technology
• Nutrition
• Dairy technology
• Agriculture
• Genetics

For more information regarding the courses after PCB in 12th, consider the link below:

https://school.careers360.com/articles/courses-after-12th-pcb

I hope this helps. Wish you a great day!