My fiancé suddenly got a sharp pain on the right side of his pelvis. What could we have done to make it go away? And what could have caused it?

Many possibilities. The right lower side of pelvis is where the appendix lies and this can get infected or twisted. Also this is a common area for kidney stone, gas distention or pain associated w hernia or urine infection. The only way to now for sure is with eval. It would be helpful to know other symptoms such as nausea / vomiting / diarrhea/constipation/painful urination/ blood in urine...Etc. Go see doctor.