Weird vein incident

[mojo jojo]

Ok so earlier I was flexing my bicep and a vein actually swelled up like a water ballon in one section about 1 inch long. It actually looked like it was going to burst. I relaxed the muscle immediately and now on my arm that 1 inch section of vein is still larger then the rest of the vein before and after it.

Does anyone know anything about this? Could it actually burst and how bad would that be if it did? Since it is Friday I can't get in to see my doctor until next week so I am looking for anyone that might know if this is serious or not.

Thanks in advance for all serious responses.