How to talk to my mom about this? Help!?

Hello, I'm fourteen and lately I've noticed A slight achy pain in my right testicle, and when I checked it for lumps I noticed a small one near the epididymis. Now I know this is is very important but it will be painfully embarrassing to ask my mom to take me to the urologist to have my testis checked. I also have a mock trial tomorrow that I can't miss. How long do you think this can wait and how do I talk to my mom about this?