Reassurance. Reassurance is number one. Secondly, if the pain is "severe", simple analgesics like tylenol (acetaminophen) or Motrin would normally suffice. Avoiding excessive sports activities, known to cause/aggravate pain may be sometimes helpful.
Supportive care. Provide support with heat pads, massage the area, and occasionally a otc children's pain medicine. The pain is real, so it needs to be taken seriously.