I think I have some weird muscle problem?

So over the past year, I have had this odd lingering and annoying pain only in the bicep of my left arm. I'm tired of it and I don't know what's causing it. I'm only fifteen and my doctor says I am nearing the end of my growth spurts. I lead an active life and my diet is well balanced. I guess I could have strained the muscle but I highly doubt it since my right hand is my dominate hand. The pain isn't burning or anything but it does spread down to my forearm. I guess the pain sort of feels like a really bad bruise along with some form of a broken bone... anyway I would really like for this pain to stop because it happens almost every night and the pain goes on for almost 10-15 minutes. No matter how much I stretch my arm or apply ice or heat to it, nothing happens. Please, someone tell me what is happening to my arm.

It sounds like you have the tendon for your muscle shortened up which can happen from repetitive use or from some other pain to it. To get rid of the pain you have to release the muscle/tendon. Here is how to release that muacle:
With your arm resting across your body in front of you take your other hand and go to the top of the muscle and squeeze the end of the muscle between your fingers and thumb. You should be at the end where the tendon is so it can be a pretty small piece you get ahold of there. Hold a good amount of pressure on it. Now relax your body, take a deep breath and exhale, then remain this relaxed. After 30 seconds slowly straighten your arm out all the way then release the pressure but hold it there for another 30 seconds. It should be released now.