Any advice with anger?

Idk why but ever since wrestling started my anger has came back and now I punches my door and messed up my arm with few scratches and skin peirceing marks and I only did that cause I was late to practice idk I'm kinda scared I'll get mad on the mat and I will hurt the other kid. Also, this sucks cause I "used" to have anger issues, but now that their back, it's kinda scary cause I don't wanna hurt people. My coach also was mad cause when I showed up to practice my arm was bloody and I told him why and he just got more mad at me bur he got over it and tapped my arm for practice. And this is the day before my class tournament.