Hi dear,
            If you Challenge your result of 10+2 CBSE exam , you only will get to know the result and it will not effect other students marks or percentage.
The Paper checking and Result provided by CBSE is done with Utmost care and under guidelines provided by the board but still if there is an error in the result CBSE provide the marks. If there is no error and claim is false no marks is provided by the board.
You can Challenge CBSE result in Two ways :

• Re Checking
• Re-Evaluation

In Rechecking only Marks are checked from first page of the answer sheet.Rechecking is verification of marks or Recounting of your marks from the very first page of your answer sheet booklet.Its check calculation mistakes only.
It also checks whether your all answers are reevaluated not checked or not.

In ReEvaluation , Answer sheet is fully checked and All answers are checked again. It is also checked that all marks are given according to the criteria specified by board to the paper checker.

Hope this helps.

Marks will be provided only to the challenger.