Suggest Remedy For Pain In Shoulders After Exercising

I was practicing flips and I guess the adrenaline didn't make me realize that I possibly tore a muscle on my left arm between the shoulder and elbow, but I do remember falling couple of times on the trampoline coming down from my flips. It doesn't hurt when I write or carry things etc. but when I have my left arm up horizontally and turn downwards I feel pain. Its been like this for more than a month now and I am worried. Is this a serious injury that will need a doctor or it can heal by itself over a long period of time?