That chain rail pin holds one of the upper timing chain guides in place. I think that is the larger guide that is shaped like an umbrella. The procedure for pulling one of them out is to thread in a bolt through a stack of larger nuts and a flat washer. Tighten the bolt against the washer and the rail pin will slide out.
Best to have the valve cover off and the guide secured. Don't want it to drop in there. However this one is easily handled.
If it is leaking you can either use some sealant , or RTV as suggested. It can be pulled out a little and resealed easily. That one is muck easier to pull out than the lower ones.
Not sure if an umbrella is an accurate description, but you will know it when you see it.