If the bolt/carrier are striking/contacting the rear of the receiver, then simply replace the recoil spring. Sticking a buffer removes the empty space and transmits the force to the rear of the receiver, when in reality, it's not even supposed to contact the area to begin with. It's simply a bandaid for a weak recoil spring.
And if it needed a buffer, why wasn't it designed with a buffer, they knew and realized the need for them before the SKS was even dreamed up, the PPSh-41 and PPS-43 both have one. Even the Finnish Suomi designed in 1931, it kind of has a crude buffer, it uses compressed air trapped in the receiver as a buffer. How many rifles through the years have survived without a buffer that a buffer is now made for? I never have found a USGI issue buffer in my M1 Carbines or Garands, but, one is made for them.
But, hey it's your money.