Depends how badly you want it and how easy it is to replace for the price you paid.
When i bought a phone on Amazon, same thing happened. Now just see how sneaky this was. The seal was not broken. But you could tell the box had been tampered with and the phone taken out, and inserted back in. Cloudtail seller as well which is just some consortium of sellers around the country.
After examining the phone i found there was nothing wrong with it. No cosmetic damage. Some firmware checks all passed. It was a colour i wanted. I got it for 5k less than otherwise i would have paid.
I kept the phone and all is well. This happened one and a half year ago.
Now decide what you want.