As per your complaint sir you might have myofascial trigger point in upper back muscle most common in official job, computer worker. You need some break in between work, you need to correct your posture during working time. You also need to do regular walk, some basis exercise, neck and upper back stretching. Your pain might be better in 7-10 days but it will take around 8-12 week to get strength in muscle. You can use hot fomentation at home 2-3 times per day along with exercise. It's better to visit your near by qualified physiotherapist for proper assessment and treatment. Wish you for good health soon.