Scar tissue
 

My QH has some scarring from when he was a Mexican rodeo horse. White lumpy patches on his whithers from an ill fitting saddle and what looks like a very badly stitched, or not stitched at all, slice on his chest-extremely lumpy.
Anywho, on one of his whither spots I noticed he had a small open sore today, about twice of the size as a ball point pen tip. I started poking at it and it looked like a hard cyst was in there and we tried squeezing it out and I tried tweezering it out, but only a tiny chunk came off. It was kind of like a pimple where the pus refuses to come out even when you can see it bright as day.
I'm just wondering if the small creamy-yellow thing that was exposed is the scar tissue under his skin that is making it so lumpy? Does it have a specific name at all?