4 Answers

Info here, best to get to the doctor though  >http://www.ehow.com/facts_5692193_upper-shoulder-back-pain-symptoms.html

Tendonitis or Bursitis I would think, the repetitive actions of using a hammer, and the statement of your maturity would make me think of this.  The fact that our muscle tone decreases as we age would make one more apt to suffer from an inflammation of these types.  With some pain relievers and rest, and anti inflammatory meds., you should improve.  I hate to say, "take two aspirins in the morning and call me", but it is that type of thing. 

You may have done something to your rotator cuff. I'm sure it's just over stressed with inflammation. Rest it, do not hammer any more. Take an anti inflammatory (over the counter is fine). Use ice to help reduce the inflammation. 2 to 3 times a day or as needed. Keep the shoulder moving so it does not lock up on you. Gentle exercises, like raising your arm in the air and doing slow gentle circles just to work the rotator cuff. Do this off and on throughout the day. Another is arm straight out, straight up straight to the side, straight down and repeat. Do this a few times until your shoulder just starts to feel tired then stop and move your arm and shoulder slightly until the tired feeling goes away, then ice your shoulder again. If it does not improve in 4 days or so, you will have to find a way to see a doctor. 

Some food to eat that help reduce inflammation are: 

broccoli
bok choy
Brussels sprouts
cabbage
cauliflower
chard
collards
turnip greens
leeks
sweet potatoes
bell peppers
green beans
green onions
spring onions kale
fennel
garlic
olives
spinach
oranges
mulberries
papaya
raspberries
rhubarb
strawberries
pineapple
guavas
kiwi
kumquat
lemons
limes
acerola
cherries
apples
avocados
black currants
blueberries
almonds
flaxseed
linseed
hazelnuts
sunflower seeds
walnuts

Fish is good to for the Omega3 

sardines
snapper
striped bass
tuna
whitefish
halibut
salmon
oysters
rainbow trout
cod
herri 

Herbs and oil 

olive oil
avocado oil
basil
ginger
cayenne pepper
green tea
parsley
sage
rosemary thyme
oregano
mint
licorice

It's tendonitis. Can be quite painful. Both my parents had it from shoveling snow......when they were still living. I had it when I was in my 30s......It hung on and was quite painful.....ruined my Christmas that year. You might find relief by going to physical therapy. It will heal by itself, but might heal faster if you go to a chiropracter, or get massage,or go to phys therapy. First, see you doctor.