Health question.. rotator cuff?

something weird,
About a month ago, I had an air brake trailer at work I had to redo brakes on and replace tires. I got the brakes done and had to whack the tires off from behind with a 12 lb sledge. I had to lay on my right side to do that side of the trailer, and on my left side to get that side of the trailer while laying on a creeper. I dreaded this, knowing how my shoulder had been feeling. But after I got them beaten off, my shouldr actually felt better for a while and didnt hurt near as bad for a couple weeks afterwards.
Yet like a few months before, I had to drive a couple of 10 penny nails into my garage ceiling joists to hang my Coleman lanterns from, and that about killed me. Standing on my workbench, 20 0z framing hammer, swinging overhead.

Not sure I could even do an MRI, as I have a rod in my leg about a foot long, inside my shin bone.