There is no concrete evidence to prove that 2-3 grace marks are given, be it for any cause. However, when I was in Class 12, our teachers used to say that generally they consider giving a max of 5 marks (as grace) in order to pass a student. Hence, if this is true, in our case you will also be given grace marks. Plus, due to the recent COVID crisis (due to less number of offline classes), the teachers and the authorities won't wish to fail a maximum number of students. They will try to pass maximum students they can. So, I shall suggest you not to worry and in most likelihood, you will pass your Physics exam.