"Struck on" in that sentence means: "the bullet reached my shoulder". "grazed" means: to touch something very slightly. There, the character is contrasting because his or her bone was broken by the bullet but the artery was slightly touched by the bullet or the bullet was very close to hit.

Struck is referring to when something hits something else. In this example when the bullet hits (synonyms being smack or collided) with the shoulder and grazed refers to when something has either bounces or glides off of something. Like grazing your knee when falling on the ground. It is not so much an impact like struck but when something moves across :)

اونجا گلوله به شونم اصابت کرد، استخونم شکست و ورید سابکلوینم (زیر ترقوه) رو خراشید ( پاره کرد)

"Struck" is the past participle of "strike". In this context it means that the bullet hit the shoulder with a lot of force. In this sentence, "graze" means that the bullet touched the artery lightly while passing through and nearly broke the surface of it. Let me give another common example using the word "graze". When someone falls on the ground and injures their knee, we say that they have "grazed their knee". However, "graze" can mean to