Sound like you strained the supraspinatus mm, one of the mm of the rotator cuff.
Rest it and use an aniti-inflammitory. Avoid reaching overhead or any painful movements for awhile, then gradually, and I mean gradually, get back to normal movements. Use ice for 20 min. on, 20 min. off, then 20 min. on again if you feel
you have over done it at the end of the day. If intense pain persists after approx
2 wks, consult a Dr.

Look on the internet for Rockwood' s exercises. Use light resistance to start out with.