I don't mean to sound rude. But it is your rifle. So did you scratch it?? That is a pretty bad scratch so you should know whether you did it or not. Did you drop the rifle on a hard surface?? How did it get there?? That can tell you which one it is.

I have never had a mark like that on any rifle I have ever owned in over 40 years. So how did it get there??

If you have any doubt then don't shoot the rifle. Shooting it with doubt would be crazy. Tom.