Sounds like the 'regular' testicular ache most people get, but usually it happens during the first month. I had it for about 3 or 4 days and it went away as quickly as it came, never to return. It could be that, or something else.. See your Doctor if its not gone after a week. finasteride isn't known to cause any persistent chronic pain except for this temporary transient testicular ache that is pretty commonly reported.
