u/Blackkat03

Hello everyone! I just started selling about a month ago so still new to all of this. I only sell new appliance parts. I sold a brand new control board for a dryer and the same day the buyer received the item they started the return. I’m not sure if it matters but the buyers return reason was “I just didn’t like it”. I just received the item back today and upon inspection the buyer definitely installed this part. I know because there is now etching on the prongs. I stupidly did not take pictures of the prongs before I sent it out. What is the best way to go about this? I don’t want to fully refund the buyer because I can no longer resell the item as new. When I go to refund there is only an option to refund the full amount. I did report the buyer for sending back a used item. Am I going to be stuck refunding the full amount? I plan to call eBay Monday morning to get more information. Thanks!