The warranty will not cover cosmetic damage (neither does complete care insurance).  You'll need to decide whether to live with the scratches or pay the cost of having the damaged part(s) replaced (though the parts are likely inexpensive, the labor to replace them may be a major factor in the decision.  You can either contact Dell for an out of warranty repair quote, or check with a local computer shop to find out what they'll charge.  
My laptop Dell Inspiron 15 5510 dropped on the table. I have warranty. 6 months ago I buy this laptop. This is my heart. Please help me. My laptop working 100% with no problems but the casing is scratched.
Inspiron 15 5510, dropped, casing scratched