Peonies prefer being moved in the fall. If you don't experience problems with water accumulation or pooling around the stalk, I wouldn't worry about it. If the sunken area is unsightly, you can lay more soil over it to even the space out. We have mild winters here and I had buried my peonies with the eyes two inches deep. I had been following the directions sent with my order even though gardeners recommend the bulbs be planted more shallowly in my zone. They all sprouted. I intend to lift them this fall, but for now, they are doing well. Therefore, I don't think adding dirt would cause problems, but I don't have as much experience as others on here. They can tell you!

Leave it as is now, and replant in the fall at the correct height. It will be fine. Al

Thanks for the input, I will wait until the fall then.