Is lump on a testicle, testicular cancer?

Lumpy testicles: No. If you are 23 then is is most likely something else. Testicular cancer hits men between ages 26 and 32. If you truly have a lump on the testicle (rare) and not on the various tubes and blood vessels in the scrotum then you need to see your physician who very well may order an ultra sound to determine what this is.

Could be if hard: Especially if non-tender. Fortunately testicular cancer is quite rare at your age, however it can occasionally occur. I have had a couple of boys of your age with testicular cancer. Should consult your Dr or urologist. Simple scrotal exam can provide answer, unless scrotal ultrasound is indicated. Diagnosis most likely an epididymal cyst or some other benign testicular or scrotal lump.