Horse with abscess? Help please!?

I recently bought a 3 year old thoroughbred horse. He has been off the race track for about 3 months, ive owned him a couple months. When i got him he still had his racing shoes on, so we had those pulled off and got him trimmed up. Its been about 2 months since. Well yesterday the vet came out for a general exam and low and behold he was lame in his front leg at a trot. The vet did two nerve blocks and used the hoof testers to determine that he was painful in the toe of his hoof. The vet dug until he got blood, however there was no puss. There is no swelling or noticeable heat coming from the foot. They did a poultice and wrapped his foot up and now he is on stall rest for 3 days. He said that if he is not better then he would have to do xrays. What could be going on? Is it a deep abscess? What are the x rays looking for? Were not supposed to soak it or anything until the recheck appointment. Anybody have something similar happen?