Oil pump cover bolt broken.
Oil pump cover bolt broken. 
You could either remove and correct as previously suggested or put some rags under the pump to prevent stuff from going in the pan and then remove the rest of the bolts on the oil pump cover. It looks to me like the bolt has some meat left so that removing the oil pump cover should expose enough bolt to grab with vice grips and then remove. Then re-install the cover and replace the broken bolt. Care must be taken to not let the gears fall out as they do have an "up" and "down" side so leave them right in place. Other option is to simply replace the pump depending on the year and mileage on the car. Some of the earlier pumps were prone to bypass failure.
I would fix it or just replace the pump since it's old. The other bolts would keep the pump cover secure, but I would think the missing bolt would cause it to leak there and decrease oil pressure.
