I think you should see your DR ASAP, this is not normal how long have you had this bump for?? You might want to hurry gods knows no boy would like to lose one of their jewels, hopefully everything is ok GOOD LUCK!!
Is it on the back side of your testicle? Do you have the same lump on the other testicle? If you answered yes to this, you might be feeling the point where your vas deferens (The tubes that join your testicles to your prostate) meet your testicles. However, if you answered no, get it checked out. Abnormal lumps on your testicles can be an early sign of an infection or testicular cancer.