how did ghost GoT get wounded so badly

If you mean Ghost from Game of Thrones , he got badly wounded in the Battle of Winterfell. In the show, Ghost is shown coming out of the battle with cuts and a damaged right ear ; the Fandom wiki notes he “lost most of his right ear” and had other battle wounds.

If you meant a different “Ghost” from a game, band, or show, tell me which one and I’ll narrow it down.