No because even though if you not appear for the exam then there is going to nothing because if you don't appear for the exam then you can not get admission based on JEE main score because your attempt is null therefore it is not necessary to appear for the exam even though you have applied for the exam but I would recommend you to appear for the exam just for the sake of experience even though if you are not well prepared for this because you have already applied and your have a chance to appear for the exam there for you should not miss this chance to have experience of the exam