Left side pectoralis, latissimus and triceps weakness with tingling in the hand
10 days ago, after three days of hard crossfit training I developed awful pain in right upper back just medial of the right shoulder blade. Pain has receded significantly with rest and NSAIDs.
However, I now have weakness in right pec, lat and triceps, right side very unstable when trying to hold pushup position. Also right index and middle finger are constantly numb/tingly. How worried should I be? Can this resolve without surgery?
There are two kinds of weakness, Yancey. The first is after an injury, either to the muscle or an allied joint; then, because it hurts, you are unable to give a full contraction. This will recover, given time, but you will have to stop for a while, or at least adjust your training schedule.
The second is more serious; injury to the nerve supplying the muscle. Then contraction isn't painful; there is simply no strength and there will be wasting and loss of a reflex, and possibly sensory change in the limb.
The thumb and middle finger don't belong to a single dermatome, so it may not be in your neck. However, along with the injury above, there are concerns obviously.
More tests are needed, like the upper limb tension test, Adsons and others. Does turning your head and especially turning to the side and then looking up cause pain? Where?
The upper back and rhomboid area are notoriously difficult to diagnose; it can be a local problem, or referred from C5.
Frustrating though it may be, either you slow down or stop for a bit, or this will become a chronic injury that will continue to nag and irritate. Add to that the neurological symptoms in your hand, and you'd better take note.
Take time to smell the roses and go for long walks, or something else.
Avoid pull downs, they especially will provoke injuries like this.