Answer:
"Me duele el brazo por el béisbol."
Step-by-step explanation:
To say "My arm hurts from baseball" in Spanish, you can say:
"Me duele el brazo por el béisbol."
"Me" means "my."
"duele" means "hurts."
"el brazo" means "the arm."
"por" means "from" in this context.
"el béisbol" means "baseball."
So, the full sentence is "Me duele el brazo por el béisbol."