You wanted to apply for what?? May be you are talking about JEE Main.Do not bother.There are still many options for you.What happens if one exam is missed.There are pretty good exams ahead like BITSAT(Birla Institute of Information Technology Scholastic Aptitude Test) etc.So keep in mind and prepare for them.But do not repeat this mistake.Remember every one does mistakes,but the one who learns from his mistakes will win