Can masturbation cause pelvic pain?

Generally,no. However, if there is a vaginal, cervical, or fallopian tube infection there may be pain associated with the masturbation process. See a gyn if it continues.
Maybe. If the masturbation is vigorous and causing irritation to the tissue it could cause certain types of pelvic pain. However masturbation and sexual activity can cause increase blood flow to genital tissue thus help with certain types of pelvic pain. I recommend seeing a pelvic pain specialist for further evaluation.