Hello, I read your message and fully understood your medical issue. It is possible that during the physical activity in the gym your have put too much tension in your back muscles or have overused them which have damaged the muscle fibers and has caused the pain and swelling. The pulled or better say strained muscles need some time and care to recover. Keep in mind the following actions in order to help yourself: - rest- take a break from exercising and physical demands - apply ice on the demaged area - use compression bandage if needed - elevate your right leg by using a pillow underneath It is thought that muscle trauma is needed to promote the muscle growth. This is an argument that fitness people use to do bodybuilding. But in your case this means that you need to increase the protein intake with diet ( fish, meat, eggs) and take omega-3 supplementations. You can try contrast shower (alternate cold and hot water during shower), salt baths and a good sleep. Do not try static stretching. The best choice would be alternating warm ups with cool-downs till your muscles get recovered. You problem is not something to worry too much. It will pass by short-time, but if you have pain which goes progressive you must see your family doctor. Hope this is helpful for you.