Pain in upper arm doing lat pulldowns

Whenever I've been doing lat pulldowns (in the last week and a halfish), I've been having a sharp pain in my left arm (not bad enough that I have to stop, but it doesn't feel good). It kinda feels like it's a tendon or something going down from by my shoulder to down by my bicep on the inside of my arm. I stretched my arm out a little afterwards while I could still feel it, and I thought I could feel it pop a little, but it felt fine a few minutes after I was done with them. Anyone know what this could be? Should I stop doing lat pulldowns till it stops? I get a little worried about doing them since it feels kinda like how my hip flexor felt when I strained it

I would take a break for a few days and when you go back, check your form.  

It could be a tendon or ligament issue. Either way, never work out in pain. Give it a few days, lift light, see how it feels.You may have just experienced a light sprain. Tendons and ligaments don't have too many nerves, so very often when you hurt them you don't even know. Typically, refrain from stretching an acute problem, unless a PT tells you otherwise, at least until the pain goes away. You'll just exacerbate the condition. I've had that problem in the past. If it doesn't go away within a few weeks, see a PT. 

Don't do that exercise for a week or two and try with lighter weights then.  If that doesn't work, wait a few more weeks and try again.  If it still hurts, go to a sports doctor specializing on shoulder or arm.