Pain killers are the only option. I was told that after three months I would feel a lot better and be able to lift heavy objects again. Six months later I was still in discomfort. I think different people must heal at different rates, but as a 47 year old at the time, I seemed to heal slower than 70 year old patients. I was up and about, walking etc within a couple of days of surgery though. It was exactly one year when all my discomfort vanished, never to return. I came off strong pain killers after about three weeks, then relied on paracetamol. I was able to kick those about a month later but there was still quite a bit of pain. Your Uncle should be going to cardiac rehabilitation where they will get him exercising.
Check with your Doc and Cardiologist to be sure, but pain and discomfort in the upper chest area is normal after surgery. Bypass surgery puts the body through quite a trauma with the sternum, ribs, muscles, nerves, etc... It will heal, but may never be as once was. 2.5 years after a quintuple bypass, I still get discomfort and numb areas at times - and it's always a bit alarming being in the upper chest area. I have learned to discern what pain is what. To help promote more efficient healing, eat healthy, drink plenty of water, take good vitamin supplements, get good rest - and get out and walk for exercise.