Quick Question About Ring Size

I’m considering having my chastity device adjusted and picked up a set of sizing rings from Mature Metal. I believe I’ve found the best balance between tightness and comfort (it’s still loose enough to slip a finger under). I tested it out for 24 hours to confirm. It feels fine during daylight hours, but at night, several nocturnal erections woke me up with a dull ache in my testicles—similar to the pain from being kicked there. Could this indicate that the ring is too small? Since I’m only wearing the ring and no cage, an erection isn’t fully blocked, which might explain some of the discomfort. I’d appreciate any advice - thank you.