It will look like this when it ruptures.
And eventually looks like this.
Danny's abscess ruptured at the front of his hoof and in the back. The entire process, obvious limp, can take days, weeks (and sometimes months) to get through and is so often misdiagnosed for other ailments that can force the horse into some nightmare (shoeing) situations.
Initially I noticed a very slight limp as Danny trotted across the pasture. Hours later, he couldn't put weight on one front leg. That evening he was down and for the better part of the next 3 or 4 days. His preference was to lay in the grass. I kept him separated from the other horses so he spent his time near the fence. Sometimes he'd roll up on his chest and eat. He was in the stall only at night.
How did I know it was an abscess? The lameness was initially slight, then it became severe in a short period of time. He never lost his appetite. His temperature didn't change. There was edema up the leg with no obvious sign of trauma. When pressure was applied, there seemed to be no pain in his leg, only in his hoof.
After the rupture, Danny gradually became more comfortable. He started walking without lameness, but it would appear at the trot. Now, a couple weeks later, he can canter but still favors that leg.
However, it will take time for the abscessed material in his hoof to become exposed in the sole area, and for the rupture sight on his wall to grow down to the ground. Below the rupture, there is no longer wall/sole attachment. As the new wall grows down above the rupture, the wall below it may break off.
What can you do while this process is taking place? Wait. I administered some pain meds for Danny while he was going through the worst of it. That gave him some relief.
For more information on this disturbing, yet ever so common condition, there is an article on my website about abscesses. heelfirstlandings.com