Thank you for your question and photograph. Unfortunately with a lipoma of that size I would anticipate some form of permanent contour irregularity along your back from the pressure the lipoma exerted on the overlying skin and surrounding adipose tissue. You will see some improvement as you heal further, but if the contour irregularity is present after 3-6 months you can contemplate fat grafting to help improve the area's appearance. Hope this helps.
In general, the larger the lipoma was, the greater the likelihood that there will be a dent (initially) and that it may persist. To some degree, this is caused by pressure on the fat that's underneath the skin (pressure from the lipoma). Fat can regenerate to a certain degree once the pressure is alleviated.
And, either way, your appearance at this very early stage is not necessarily exactly what you'll look like once you're fully healed.
You should of course discuss this with your own plastic surgeon for a full and complete discussion.
I hope that this helps and good luck,
Dr. Alan Engler
Member of #RealSelf500
Usually, but not always. Everyone heals differently. The less traumatic the dissection, the better the result. The posterior neck and back are difficult locations because the lipomas are usually multi-lobulated making them difficult to remove, and difficult to apply post operative compression. A negative pressure drain is a good choice.
Time will tell.