First, WHY do you have this pain? Backing off on your exercise program might be required. Steam is very efficacious, as is warm or herbal wraps. Massage is VERY effective. You have to analyze if you have injured your muscle group, or if you just have a strain.
Pain may result due to stress, work or home areas that aren't set up ergonomically, stress, and exercise. Gentle stretches, massage, heat, and strengthening exercises can help the pain.
for trapezoid muscle pain,contrast bath is the best self treatment. contrast bath means hot water and cold water fermentation. you should give alternatively hot and cold water massage. so that there will be new blood circulation. after this,there is no accumulation of pain metabolites. pinching of that muscle continuously for one minute will also relieve pain. this treatment is known as myofascial release therapy.