Would genioplasty correct pain and stiffness from chin implant?

It is unlikely that a chin implant will get infected 4-5 years after being placed but it is possible. You should return to the surgeon who placed it to be evaluated. I recommend a CT to evaluate the position of the implant as well.

It’s pretty unusual to develop problems for years after the placement of a chin implant.
I suggest you follow up with your provider schedule in person consultations with other plastic surgeons or oral surgeons in your community.
It would be unusual to develop a clinical infection this far out after surgery.
There are possibilities of sub clinical bacterial growths that can cause capsular contractions of foreign implants from the bacteria Staphylococcus Edpidermidis. Confirming the presence of the bacteria is difficult and it could generally not be treated with antibiotics.
The radiographic evaluation is probably in order.
In regards to clinical background, oral surgeons may have a slight upper edge, but in the end, it depends on a clinical experience.
Best,
Mats Hagstrom MD