let no one cause me trouble: No one has the right to criticize Paul or his message because he is a proven servant of Jesus.
Paul's scars (in Greek stigmata) likely came from the severe persecution he experienced as a servant of Jesus (see Acts 14:19; 2 Corinthians 6:4–10; 11:21–33). Unlike the physical mark of circumcision that false teachers in Galatia wanted to force on non-Jewish Christians, Paul's scars from suffering showed he was truly the servant of Jesus (compare Exodus 21:6).