Hello dear candidate,

Hope you are doing well,

Yes, you can definitely leave BAMS and if you want to, you will have to drop that year and start from fresh in MBBS that is from 1st semester itself.
You can't migrate from BAMS to MBBS directly, So, as this will be fresh start in MBBS. There will be no sort of penalty as such.
And, If you are transferring your degree from BAMS to MBBS in the same college or university, then certain rules of University will occur as program exchange fee or some sort of thing which varies from college to college.

If you are changing your course within the college only, then you can enquire the formalities from the college as well.

But if you are pursing a fresh MBBS from different university or college, then your one year of BAMS will be dropped, else no such fine will take place most probably.

Hope this would help you,

Thank you.