Ice or, at the least, cold hosing for 48 to 72 hours on any new swelling, hot spot or lameness. NEVER heat or liniment.
If you apply anything, it should be DMSO, which is an anti-inflamatory and should give Bute if it is available. We do this the minute we find a new injury. Then we contact out favorite lameness Vet.
Here is the regimen our expert lameness Vet has us do for any fresh hock injury. Obviously, you should call your Vet that specializes in lameness and follow his/her directive. But, this is what ours has me do. By the way, we live in reining and cutting horse country, so we have Vets that specialize in hind limb lameness.
If a hock is swollen, I palpate it and determine if it is fluid causing the swelling. A bogged hock will have a bulge of fluid in the front of it. It will bulge out toward the two sides further back when you push on the front. You can literally see the fluid move. In that case, I wrap it with pads of cotton on the front and over the sides where the fluid it. This keeps it from getting much, much bigger and taking a lot longer to get better. Then, I take the horse to the Vet to have the fluid drained and he will inject the hock and direct me to keep pressure on it by keeping it wrapped and to keep putting DMSO on it.
If it is general hock swelling without fluid, you probably have a supporting ligament damaged. This can be much more serious. My Vet would want me to still use DMSO and icing several times a day and give BUTE until I can get the horse in to his clinic. If it is a valuable horse, it would probably mean MRIs to find the exact ligament damage and could mean the use of stem cells or some other very expensive therapy. Saddle horses wold be continued on DMSO and Bute for a week or two and then be turned out for 6 months to a year.