How can I prevent my hands from getting sore when I punch the bag?

Wearing boxing hand wraps properly will help, as will wearing the right size gloves. Also, make sure your gloves have good padding, which will help absorb the impact. When you punch, strike the bag with the knuckles on your middle and ring fingers. Doing so will align the force of your punch with the weight-bearing bones in your forearm. In time, the tendons and soft tissue in your hands will acclimate to the contact.