I figured this was another technical question about site changes and thumbnails for pics.
I am not a doctor and I haven't really mashed my thumbnail good before but I did kick a half-buried pipe by mistake while walking across a field and it broke my big toenail, which is basically the thumb of your foot. Ideally, you just mashed yours and it hurts, rather than having broken the nail beneath the cuticle. If there is bleeding beneath your nail, you may need to relieve pressure. I wound up drilling in carefully with the tip of a sterilized knife. I would only consider this if there is substantial blood showing beneath the nail and if swelling and pain persist into the next day and beyond.
If the nail is broken, you will have to let it grow out to fix it. I suspect the risk of an ingrown toenail is higher than a thumbnail given the pressure and very frequent use. Still, keep an eye on how it is growing out if it has broken. You may have to cut it to the quick (ouch!) in order to keep it in line and get it back on a healthy growth track.
I sure hope none of these complications arise for you and it will feel better in a day or two.