Nails always grow back unless the base of the nail is removed, which generally is a surgical procedure, as its located behind the visible nail under the skin.
I've lost nails before. I habitually pick my finger and toenails. I managed to rip down the sides of both my thumbnails before, down the side closest to the adjacent fingers. It left a big hole over the nailbed which unfortunately got a small infection. A large green blister-like pocket grew over the hole and filled with pus. They eventually burst and the nail underneath grew back.
Thumbnails grow back the slowest of all nails and can take a couple of weeks to grow back fully. The thing that lasts the longest is any bruising to the nailbed, which tends to last quite a long time and can be a bit sore.
If you do have exposed nailbeds then it's best to keep the thumb and hand clean. Wash it gently with warm water just to ensure you don't get anything in there to cause an infection.
Other than that, just try to avoid knocking your thumb. It'll hurt an awful lot.
You may also find that if the nail is ripped and in two separate parts, but attached to the rest of the nail, then cutting off the loosest part towards the end of your mail at be best. The exposed edge of the hanging nail can slide underneath the other part and cut the nailbed.
When the nail starts healing a little I'll probably cut off the hanging part and allow it to start healing properly.
This is going to suck..
Never mind, I talked to someone whos had it happen. I can just let it be.
