Sounds like you have a high spot Eric, (redundant), that means you have to much metal in that area and you need to shrink it. Hammeing on it with a dolly only thins the metal out and stretches it out more. If it is a small area (silver dollar) you may be able to apply heat with a torch and quench it with a wet rag, try that a few times and it may bring it back. If it shrinks back to far then you can dolly it out smooth. If its a very small area (fingernail) you may be able to use a dolly that is slightly concave and tap the high spot down into it. Don't beat on it, it only takes a little pressure to reshape a thin section so just tap, tap, tap.
If its a large area and it sounds like it is if its oil canning, then you might concider a shrinking disc. They are cheap and work by heating up the metal by friction. Down side is it takes a little practice to get the feel for it. Denny Graham
Sandwich, IL
