Is there still a possibility that I regain nipple sensitivity if it's been a year and 6months after my breast lift?

At this time after surgery, you probably have damage to your nerves and sensation probably will not improve. I doubt PRP will be of much benefit, but it could be injected to try if you want.

Changes in sensation are one of the risks of surgery. Typically sensation improves within the first year after surgery as swelling resolves and tissues heal. Sensation changes that remain after twelve months can be permanent. However if you are still noticing improvement it may continue to do so.

In most, but not all cases of sensation loss after surgery, the improvement in sensation will have
returned by 1.5 years. This is not always the case and some people report gradual improvement, extending out to three or four years. Patience is on your side. I know of no evidence that a PRP breast lift will help with sensation return.