Oil leak from behind timing belt cover

I've just bought a toyota corolla 93 1.3 xli hatchback recently and the car was in really in good shape with not so high mileage. After about having it for a month it started leaking oil from behind the timing belt cover and I have no idea from where exactly it started leaking because i'm that handy with cars sadly. So i was hoping you can shed some light on my issue.

The weird thing is that the oil was only leaking for a about one week or so, not longer than that. After it stopped leaking I checked all the fluids to try to diagnose from where/ what it was leaking but everything was where it should be.
The car starts without any problems and the oil signal doesn't light up while the car is running so I don't know what really happened over that week.