Stretch the chest - Stretching the pectoral muscles is the second stage of the physical rehab you will do, if you stretch your pectorals against a door frame or wall, you are further aiding in the strengthening process of the upper back and bringing those shoulders back where they should be. Again, YouTube is an option with this as there are many easy demonstrations here.
Move from your computer at regular intervals - I recommend every 20 minutes to be optimum, even if it is for 30 seconds. This will make all of the difference as your muscles are mobilized and are not frozen in one position. It also helps to change your seated position too on a regular basis.
Use deep freeze - using a cooling lotion or indeed a bag of frozen peas can make all of the difference too, as you are reducing the inflammation of the problem area and flushing fresh blood through when the cooling effect is removed