I had the two Moderna shots. From an informal talk with friends, it appears the Moderna shots cause a bigger reaction than the Pfizer shots.
My first Moderna shot, not such a big deal. The arm felt a little sore. The second shot, a much sorer arm, if I moved it, chills and a fever up to 101.5 degrees. But the worst of it lasted only 3 hours. No big deal. And it was all over after 27 hours. A much lesser deal than even a mild case of COVID-19 itself.
Get the shot in your denominate arm. The more you move your arm, the more it will hurt (temporarily) but the sooner it will disperse the vaccine from the area causing the arm to not hurt anymore. No need to lift weights or anything. Just use your arm as normal and ignore the pain. Pain killers, even non-prescription, can, I understand, interfere with the effectiveness of the vaccine.
Lots of people are hoping that enough people will get the vaccine, they can skip taking it and get away with it. Too many people are hoping that. If you don’t take the vaccine, the virus will find you, sooner or later. Save yourself a lot of trouble and just take the two shots, or one of Johnson and Johnson.