take the bolt out, and cut a piece of copper wire.  strip the insulation off of it.  wrap the copper wire around the bolt and carefully stick it in the hole and start turning.  usually the copper is enough to smush around and give it some bite.  you should be fine if you can get it to snug up. start it on the trailer for a quick second and spray a little soapy water around the port and see if you get any bubbles.