Is it possible this is just a reaction to the sutures? Also, sometimes sutures work their way to the surface...maybe that is what is going on. Hopefully, that is what this is. I would definitely take him in for a follow up....I don't see how they could charge you.
You need to put an E collar on him if he is licking...that will cause more irritation!
Keep us posted. I am sorry it has been so difficult.