Hopefully this is a small flare up and will dissipate quickly. I have had problems with carpal tunnel but only with small motor stuff with my hands or holding in a position for too long. The worse was when I drove my atv for long periods of time and keeping my thumb on the throttle would bother it. The only I can think of since it popped up on squats is that maybe it is bothering your bicep tendon from being pinched in the shoulder. Ever try putting your pinky finger under the bar when gripping the squat? I use to do that years ago and it alleviated shoulder/bicep tendonitis because you end up not pushing on the bar with your hands because it is uncomfortable. It may be worth a try to see if it helps. LEt us know how your ultrasound etc turns out.