You might actually be escalating the behavior by separating your chick from the others. They have pecking orders the same as adult birds do. Removing the chick and then putting it back with the others may be upsetting the balance and making your little tiger fight for what it perceives is its rightful place in the order of things.
I have 8 2 week old chicks hatched by a Buff O hen. They are to the point where they are scrapping with one another from time to time. It's comical to watch them jump and fly at one another in mock battle. If somebody gets too rough, they just run back to momma for protection.
As suggested, I wouldn't worry too much about it as long as no blood is drawn. Don't permit it to act aggressively towards you however. It might be a little cockerel and no sense allowing bad habits to set in that you have to deal with later when it is older. I've picked up chicks when they act out towards me and held them till they calm down.
Good luck with your little 'slugger'.