Why does my dog growl at anyone who comes near me?

I have a male chihuahua. He is mainly outside , but I bring him insides every night because he barks a lot. He mainly barks at people he does not know, but the people he does know he shows affection. However, ever since I got an ankle surgery on my left leg he has been growling and snapping at anyone who comes near me. Is this over protectiveness? If it is , is there a way to stop him from growling and snapping at people? I've tried telling him no and moving him, but he still growls at people who go near me. He also sometimes sleeps with me on my bed.