Depending on your stock, there is probably a nut for the swivel stud in the fore end. If you remove the barreled action from the stock, you'll see how the stud is attached. You can get the new stud and nut from Midway or your local gun shop.
If no nut is present and it is just a hole in the wood/plastic there are epoxy glues that can be used to fill in the hole and it can be redrilled to accept the stud.
If it has a nut on/in the stock see if it is stripped if so it can be replaced.
Yep. Fill the hole with epoxy, bedding material is best, and re-drill. Put a piece of masking tape on the outside and fill from the inside. Reduces the amount of sanding required.