With your lower eyelid drooping, you may very well have some eye irritation due to corneal exposure and drying, which can contribute to swelling. Your surgeon can give you some stretching exercises and instructions on how to prevent drying at night, which will help your eyes feel more comfortable, and may help with swelling while you wait it out. For now, the best treatment is tincture of time. Usually the drooping will resolve with time, but it is possible that some day corrective surgery might be necessary if it does not resolve. Lower eyelid surgery can sometimes have a difficult recovery. Keep in close contact with frequent followup with your surgeon. Good luck.
Swelling is typical after lower lid surgery, though for most it will last only several days. Talk to your surgeon about lid massage, or perhaps tape to support the lid until your swelling improves.
It is hard to comment without seeing a picture or an in-person evaluation.
Your plastic surgeon may consider using massage, tape, or a suture to help control this.