Just for the record, let me reiterate that I am not a doctor and never have been one (or have claimed to be). As such, I am not contradicting the advice of the people who are telling you to go see a doctor.
They are correct.
What I am is an educated parent, which is something that I suggest that the parent of every pitcher (at least) should become. The problem is that many doctors and coaches have only a minimal (or worse yet incorrect) knowledge of the impact of pitching on the body or injury mechanisms and as such often give out bad advice (e.g. what they have heard, not what the studies say). As a result, it is in your interest to learn everything that you can about the physiology of pitching.
One place to start is in the Q&A files of Dr. Mike Marshall (http://www.drmikemarshall.com). In these files he talks in depth about the physiology of pitching. Once you have done that you might want to start googling around for phrases like "little league elbow" and "reduce risk injury pitching." You will come across multiple studies that are accessible over the web and that help to explain what happens to young pitchers and why.