Hi Aspirant,
Well,if you don't appear this year there's no problem in appearing the next year.
You can appear both as a student in a school or as a private student.
However,why do you want to waste 1 year of your precious time?
For the boards which take place in March,you have sufficient time to study and Excel even if you hadn't done anything till now.So,don't think about wasting a year.You have got sufficient time to study and start your preparations right now.
Do well.
Hope this helps.

Hello Ayush, 

Well there will be no such problem if you will not appear in 12th board but there are some institution which consider this thing for admission purpose. Also there is so much of time left that you can definitely prepare for board exam because exam take place in month of march and you can easily start your prepration, work hard and appear for paper. 

All the best. Do not lose confidence and if you wish than you can definitely appear for the exam also will able to clear them with good marks. 

Dear Ayush Kumar 

If you don't applied this year you don't pass the exam and you will be failed 

Don't think about not writing your exam .if you only prepare for your exam time you can still pass just think like this this is just a 12th exam .if you work even in the time of exam time you can still pass the exam 

Don't lose hope 

Best of luck