If you get your thumb closed between two car doors, by all means go back to the house and don't play tag with the rest of the birthday guests. Take the ice and painkillers offered by the GOH's mother. Call your parents to let them know what happened, and take their advice over the phone. Ignore what the people who are in front of you and can see the damage are saying.
The next day, when your parents finally see your thumb, which has a rather large dent just below the cuticle and is swollen somewhat epically, continue to listen to them when they say it's not worth going to see a doctor. Even when the nail falls off.
To this day, I don't know if I actually broke the thumb or not, I never saw anyone. Dad convinced me that they'd only be able to tape it and give me painkillers, it would have only been the tip of my thumb. I think I did, though, because I can feel the weather change, and that knuckle has been able to pop funny since then. Oh well.
When I was 8 or 9, I was on a softball team. First practice, all us young girls with no clue what we were doing and crazy stiff gloves, we were taught to catch the ball in the glove and then cover it with our other hand so it wouldn't fall out.
I, being the uber-brilliant 8 or 9 year old that I was, extrapolated from this that if it was good to cover the ball to keep it in, it would be even better to help
it in with the other hand!
...not so much. Most likely broke the thumb. Shoved it in a water bottle full of ice water to prevent swelling, the nail turned black and fell off a month later, and then the knuckled popped. Every. Time. I. Bent. My. Thumb. For four years.
At age 13, it's so bad that I'm bending the thumb to hold on to a pen, and leaving it bent even when I let go of the pen, so I don't have to deal with the pain of popping it straight and then bent again. We finally went to a doctor who informed me that it's chock full of scar tissue so the tendon doesn't have room to slide through (? past?) the ligaments and we can do surgery now to cut out the scar tissue or wait. Until the bone itself pops out of the skin and I need 5 or 6 surgeries.
Yeah, I had surgery on my thumb then.
So I feel your pain, cwm. And if your popping thumb gets too bad, get it checked out!