I was picking out my horses hoof and noticed there is a soft spot in the heel. It occurs in the crease that runs from the back of the heel up into the hair line. I'm not sure what this crease is called but I can actually slide the pick all the way into the crease. The other three hooves are not like that. Any suggestons? Is it something to worry about. It seems like a rock could easily get stuck in there.
Without a picture to be sure, I think what you are referring to is the sulci and yes that is something to worry about.
Black and smelly indicates thrush, which is what the other poster was asking.
Deep fungal infection in the sulci doesn't have to smell, but it is there. I fought it last winter on not one but three of my four horses on their front hooves
If you don't have time to soak the hoof in some kind of "dyne" (povidine, betadyne, etc.):
1) Buy a couple bottles of WalMart's brand of povidine.
2) Buy a stiff-bristled and easy-for-your-hands-to-handle fingernail brush.
3) Carefully clean out the sides of the frog with a pick, then very gently pick the sulci area (the area you are describing), without running the pick down in there.
4) Then gently brush that entire area with the fingernail brush. If you horse will let you, gently run the edge of the brush a SHORT way into the sulci.
5) Once you get all the debris removed, pour the povidine down into the sulci, over top of the frog and along the sides of the frog.
Again, from the sounds of what I think you are describing, that area really should be soaked a couple times a week but still pour the povidine down in there every other day until it starts growing closed.
It's a long story why my three of my horses ended up getting that bad, but it happened and I ended up soaking three sets of front hooves every night in warm water, a capful of clorox and a couple tablespoons of Triodyne which is 7% iodine.
I then had to put ToMorrow down in the sulci, and top that off with diaper rash cream to help keep the ToMorrow in there. I did this 2X/day.
All this regimen went on for one month, then I got to quit the soaking, but still had to apply the ointments for two more months.
My horses come in at night, so after that grueling exercise, I decided every time it rains, the horses get povidine shot into the sulci/frog area whether they need it or not.
Hope this helps and pictures would still be good