Your Dr. is correct, you may need a revision or if a hematoma or seroma is present it may need to be drained.At this late stage in your recovery and based on your photographs my guess is that you have residual loose skin and will need a revision at least on that side to further tighten the neck skin.
This early on many many patients will have spotty swelling so stick with you doctor for frequent checks. Often I will try a soft compression neck garment to use at intervals. If it is serum or blood collection then over a few weeks it should disappear. As a longshot I have had one patient with swelling in the submaxillary gland, just under the jawline, where your photo has a small lump. She had a small stone in her duct which had to be taken care of by removal from under the tongue. Very unusual. Anyway, my thoughts are that this is likely temporary and will slowly resolve. Best to you.
Thank you for your photos. This may represent swelling, a fluid collection or your salivary gland on that side. Exam is going to be the key to answering this question. There should be no rush to revision. Wait three months it is surprising how things can change in that amount of time.
The best way to decipher what this lump is, would be with an exam. If its soft and just feels like loose skin, then that is most likely what it is. If its hard or feels like there is fluid in there, then it may be fluid or blood. Your surgeon will be the best one to tell you what it is and what can be done for it.
It is not uncommon to see lumpiness right after a facelift. Bruising and fluid can both contribute to what you see. It may take several months for everything to resolve and stabilize. Your surgeon is best equipped to explain what was done and what to expect. Followup with him and ask questions.