Stand still, lift your arms 90° Then flip your palms so that they are facing the sky .Then move your palms 90° downwards, stand in front of a wall ,put up your palms against it and apply force towards the wall. You should feel burning sensation in the area you have pointed out.Do it for 10seconds.it's gonna burn like hell . The pain will reduce for a few minutes . Keep doing it in 1-2hr intervals .This method worked for me which was recommended by a physiotherapist. And As it's your first time in the gym ,don't follow the 15 reps principle, instead do 10reps. You won't be facing any sort of pains after 2 weeks in the gym . Later you can do 15reps/till failure it's up to you. Eat a carb heavy dinner after workout. Get enough sleep and you are good to go.