MRI
definitely get an MRI, but it sounds definitely like a tear, even if only partially. if it were a full tear it would hurt a lot more. i had the same thing a few years back. tried to continue lifting through it but i only made it worse and it just wouldnt heal. so i had to take a complete break for a few weeks, then finally it healed. also went and saw a chirco twice a week, and i also did a nice rehab movement which consisted of taking a towl and holding one end close to my lower back behind me, and the other end above my shoulder (hard to explain without showing you) and basically pulling down with my one arm and pushing against it with my ogther arm which is placed over my shoulder. Basically a simple tricep training exercise, sort of. and then keep going back and forth. helps with the pain and a great rehab exercise. that and REST helped me heal, although the resting part (and not working out or at least not heavy) was what did the trick. hot packs and ice packs are okay, but it just needs a bit of time.