It is ok if you haven't prepared well. But if you have prepared atleast few topics, keep revising them so that you score decent marks. Learning something new in the last minute will only confuse you further. You might be lost. So stick to NCERT and attempt as many as mock tests as you can. Noe is not the time to learn anything. With hardly 2 days left, you can atleast attempt 10 mock tests if you are serious about NEET. That way you will be able to answer on the day of examination And on the 13th, do not attempt a question whose answer you are unsure of. You do not want your marks  being taken away in the form of negative marking.