Keep the bass and take the marks out...it is an easy and cheap job to do.
No offense, but I have to agree with Fergie Fulton. I've bought several items on Reverb since 2014 and only had a problem once due to blatant misrepresentation. For your situation the seller listed the item as mint, which is not new. I do not know what the rest of the bass looked like, but those (2?) very small dents on the back of the neck that don't appear to penetrate the finish of the bass are barely visible/extremely minor in my opinion and are only visible to the player and only under scrutiny. Mint is not new. It is hardly 'terrible'. Did you pay close to new MSRP?
The problem I had on Reverb is where the seller substituted a soft case for a stated hard shell case. After the sale the seller contacted me and said he couldn't ship the bass in the hard shell case made by the manufacturer that he stated in the Ad so I replied 'no big deal as long as it is still a hard shell case, I don't care who it is made by'. When I got it I told him I wanted a refund and immediately contacted REVERB. I got my entire money back, including shipping.