Hi,
As your Pain is chronic i.e more than 1 year . Try doing Hot Fomentation for 10 mins three times a day . Take muscle relaxant medicine Tab Thiocholchicoside 4 mg Twice a day for 5 days . Try to note weather pain is increasing while breathing.
Next Steps
If it is not subsiding then you can go for a small procedure in which nerve supplying the particular muscle which is paining can be desensitised with help of injection. For which u can visit nearby Pain clinic