I have a large squishy lump under chin on left and right hand side of neck, 2 weeks after a neck lift. Any suggestions? (photo)

I can certainly understand your concern. I always suggest to my patients, if they have any concerns during their healing to call me and discuss those #concerns. I encourage you do the same to your doctor. Meanwhile, perhaps this may provide clarity on healing expectations.
Though recovery from a surgical #necklift varies from person to person, patients are generally presentable within three weeks from surgery. Generally, it will take approximately 7-10 days for the early healing in which many patients feel comfortable being in public at this stage. Most #bruising is low on the neck and may easily be covered by clothing. Also, wearing a #compression garment may be suggested the first week and then nightly for up to six weeks.
The #incision scars from a necklift can typically be hidden well and are not located within eye level to be immediately noticed. These #scars “mature” within six to twelve months from the surgery date. The term mature implies they will soften and fade away. During this time, the rejuvenating effects of the necklift will become most obvious and the neck feels the most normal (ex. little discomfort, soft, normal sensation, no more post-op firmness). Following this stage, the true restorative effects of your necklift result will be apparent.

It sounds like seroma collection under the chin area. You need to speak to your doctor for help. It may require aspiration of the fluid. The firm area is swelling. 

I suggest speaking to your physician, however, I have found many patients benefit from botox and venus legacy treatments of the neck after surgery. If this is a seroma, which is a collection of fluid, aspiration, neck compression and radiofrequency treatments will help.  Best, Dr. Emer.