Hello,
Is your product under warranty? If the answer is yes; You can call Dell Service and get information about the problem.
If the answer is no; Check your computer model from the Dell support page. After finding it, enter the manual guide page. Please review the problem/solution articles about the screen in this area.
Finally; You can use the Dell diagnostic software (Support assist). Or there is definitely a diagnostic feature at startup, you can test it from there. If it is faulty, the software will tell you anyway.