Try some neural "flossing" first if your physio deems it appropriate. Neural stretching can aggravate the nerve in some cases, and while it can be effective, should start out very light and progress as tolerable. Some light thoracic stretches may also help over a period of time. While improving your neural pathway, you will want to take as much tension off your nerve roots/peripheral nerves as possible to decrease irritation, this means good posture, shoulder position and mechanics, reducing aggravating factors etc. A lot of Vanc_WA_PT's information is great in terms of exercises to be wary of.