I've adjusted my desk so I sit properly 2 weeks ago - now my shoulders hurt

Before the adjustment, I've been sitting with the desk too high and keyboard and mouse too far into the desk (by ergonomics standards) for many years and never had any issues. Around 2 weeks ago I adjusted my desk so that my knees and elbows are at the proper 90 degrees with my shoulders hanging instead of having them raised like before.

I've since developed consistent shoulder pain. I can feel the pain the most when I push my shoulders downward and back.

Has anyone had the same issue? Is this just my body adjusting to the proper position?