okay, i shadow boxed recently for the first time in a while and i'm not sure if it's normal to feel sore at the point where you bend your elbow (not the elbow itself but the tendon inside it i guess) This content is protected
Thats a nice picture of a left rib cage thanks for showing it me. But to answer the question most likely your body is just not used to the strain from doing nothing to constantly have to retract at its quickest for hundreds of times in a matter of minutes. You should rest it and then try it again when its healed and it should not hurt as much or if at all. That or your punching with terrible technique or using hand weights.
if you do anything physically demanding you haven't done for a while there will always be some degree of soreness.
It's not a good idea to shadow box with power especially for the first time because it can mess up your joints and mess up your technique. When you first start out with shadow boxing just focus on being quick and loosen up your entire body. I've been boxing for about 6 months now and when I first started I was very powerful on the heavy bag because of all the muscle mass that I had. When I shadow boxed and sparred though I would try to throw every single punch with power also. There was some problems with this though. I was way to tight,way to slow,and way to sloppy with my punches. I think that it's everybodys instant reaction when they first start shadow boxing (or sparring) to start throwing every punch with power because your ego is telling you thats what's best. That's really not the case though. If all your doing is throwing power shots your opponent will see them coming from a mile away. Just focus on speed and relaxing when shadow boxing and when your in the ring. Then when you get better you can focus more on power shots. I know that this post is slightly off topic from what you originally asked but all this stuff really helped me when I started showdow boxing so I just thought I'd throw it out there.
Your elbow is probably sore because you were throwing too hard in shadow boxing. You need to be careful when you are only punching air because there is a tendency to snap your elbow too hard. Concentrate on technique, not on power.