Hello aspirant

You can find many candidates who scored 50 to 55% in PCB but they scored good in neet.

Eligibility to appear neet - the candidate must score minimum 50% marks in Physics, chemistry and biology

Eligibility for admission to MBBS or BDS/ medical course - The candidate must have passed xii board with minimum 50% in PCB subjects and must have qualified neet exam.

So you don't have to bother about your xii STD marks , you just have to secure 150 marks in PCB subjects. But one should not take it granted as if you are not clear with theory part then it will be difficult to cover neet syllabus. You must try to do your best .