Hey Cade, did you ever get this pain diagnosed? Hope you're feeling better!
There are lots of reasons for this to happen, and the only way to know is to see your doctor.
It might be epididymitis, a hydrocele (unlikely with no swelling), hernia, spermatocele, kidney stones, etc., etc.
You need to see a doctor to find out why. I know health anxiety makes things really scary, but you really should find out.
https://www.mayoclinic.org/symptoms/testicle-pain/basics/causes/sym-20050942
Let us know what happens.