It usually happens at night, but it does happen during the day. There's some pain right in the left side of the testicle, but not on the lower testicle, more right below the penis, right on the side. I don't feel any lump, though I could be wrong. It's happened for the past few nights. It could be swollen, but I'm not too sure. What could be some causes of this. I'm hopefully going to see a doctor in the coming days about this. I'm hoping it's not cancer, so I'm wondering if there could be any causes for this pain.