This is at the top of the front half of the engine. Theres a little circle thats full of dirt with a hole in the middle of it.
It's very had to work out from the picture where on the engine this is but my guess is it is a threaded hole for the bolt the holds a plastic cover or it's unused. If you look at the same spot on the other cylinder it will either have a bolt attaching something or not. If it turns out there are both empty them you might need to go looking for a missing part.