What Causes Sharp Pain At The Surgical Scar On The Back?

Hi , I had a lump removed about 15 - 16 years ago on my back up near right shoulder blade , for a little while now I have had a pain near the scar , almost like a warm knife pushing from inside my back trying to get out , when im rested it doesn't hurt but going back to work after holidays its now hurting again . Im not sure if its tissue tear or muscle related .