I agree that pecking at hands that are moving within the vicinity of a chick may very well signify the chick is a cockerel. In that case, you need to begin behavior modification immediately or risk having a problem in a few months when the cockerel comes into his hormones. A poke on the back each time the chick engages in unacceptable behavior will go a long way toward modifying the bad behavior. If the chick isn't responding to this discipline, if the chick is closing in on sexual maturity, you may need to immobilize the chick until it submits. It's never too early to begin disciplining a male chick when it displays aggressive behavior.
Understand, though, that all chickens use their beaks to explore and to communicate. It does not necessarily indicate aggression. You'll soon find out the difference between aggression and simple communication as you spend time with your chickens.