Lipoma removal does require some post op downtime. Dependin on the surgery, I would suggest about one week.
Thank you for sharing your question and I hope that your procedure goes well. Unfortunately without knowing the diagnosis of your mass, nor the exact procedure to be performed, it is difficult to offer definite advice. If your lump is a lipoma, the pain from surgery typically lasts only a few days and then can be managed with Tylenol or ibuprofen alone. Your surgeon should be able to offer you the best advice. Best wishes.