I was doing my warm-up set for squats this morning and at about my 5th rep m bicep started to sting pretty bad. I racked the bar up and looked down and the main vein that goes down the center of my bicep was bulging in an abnormal way and looked all twisted and "s"shaped . after a minute or so it smoothed out but had a few bumps in it, and by the time I was completely done with squats it had smoothed out back to normal and just looked like my usual vein. has anyone else experienced this or know what could cause that in a vein?? It kinda tripped me out for a bit and really threw off my focus.