Neck/chin Lump 2 Months Post Face-lift? Felt Pop After Sneezing Attack

Without examinating you and touching the area of concern, it is difficult to judge what exactly is going on.

A localized blood collection will get better over 2 months.
A hanging salivary gland (a.k.a. submandibular gland) feels commonly similar to a large but soft grape. Your surgeon has the benefit of knowing what he has done surgically and how your progressed during your recovery.

He would also initiate the correct referral if your surgeon would be concerned about a malignancy.

I agree with your doctor.  RELAX.  The chances of cancer are extraordinarily remote and the risks of waiting for improvement are analogous to the likelihood of being struck by lightning.  Give yourself a few more months to hea.l Only if it persists at its current size at 6 months should you consider further tests, in my opinion.