With 21 percentile, it will be very difficult to get a seat in BSc Nursing through central or state government counselling, because cutoffs are usually much higher. In most states, even private colleges take students with at least 40 to 50 percentile or more, depending on availability.

With 21 percentile, you may not get a seat in the first few rounds of counselling. Your best chances would be in the last rounds, where leftover seats are filled. These are usually in private nursing colleges, and admission depends on how many higher-ranked candidates have already taken seats.