Slight bump showing on testicle-- do I have testicular cancer?

See your doctor. It is not possible to provide a meaningful answer from the information you provided. It would be prudent to see your doctor.
Uncertain. The typical age is in the late 20's to the mid 30's. Varicoceles, hydroceles are some other non-cancer things that can cause bumps. If it is tender or persistent, or growing, talk with your doctor to see whether you need an ultrasound to know for sure.
Get it checked out. Most testicular "bumps" are benign, but rationale for scrotal self eximination is like with breasts in women, all lumps are cancer until proven otherwise. Simple scrotal ultrasound will give the answer.