Yes he's OK. Remember the candy that Tia gave him when they first met. It was actually medicine for the Poison. Also before Tia left she told Perez to practice swordmanship and he gets so good at it that he's the first ever person in history to master sword aura at 13.
I'm legit about to magically teleport myself in the story and beat his ugly ass up so bad, I bet I'm going to smirk when i beat him up