I have a little lump on the bottom of my left testicle. it feels like a little line and it's a little sensitive. what could it be? cancer?

Vas, probably: I'll bet you just discovered your vas deferens. It's tender and a tough cord. Some guys have it down there. If the mass starts to grow, get it seen. For your acne, topical benzoyl peroxide 5% 2x/day is your best friend; if you're not clear, get with your physician the same time you show him your testicular finding.

Exam: If you find something on self testicular examination that was not previously present, you should show it to a physician and let them them examine you. It's quite possible however, that you're feeling the normal epididymis.