You’ll need to keep a close eye on your oil level.
Engines don’t die or sustain damage because they have an oil leak. They die or sustain damage because the owner doesn’t monitor the oil level and it drops below the level of the oil pump’s pickup tube, causing loss of lubrication. Their lives can also be shortened if they’re continually operated with low oil. A given amount of dilution is more damaging mixed into two quarts of oil than it is mixed into four quarts of oil.
The oil (lubrication) system is not a totally pressurized system. It operates by the pump pulling oil from the “pool” in the oil pan and pushing it through the spaces between the bearings and their wear surfaces. That forcing of the oil through the oil channels causes pressurization of that portion of the system, but once the oil has performed its function it drains down back into the pan to be reused. Pressurization of the crankcase is only a byproduct of normal “blowby”, which comes from combustion gasses being forced past the rings and pressurizing the crankcase. That pressure is normally dealt with by the Positive Crankcase Ventilation system allowing the pressure to be relieved and the gasses reprocess by the engine.
You can run the engine with one screw missing, but you need to monitor the oil level and ensure it doesn’t run low. However it’s always better to chase he hole and repair it. Note while dong that this is a “blind hole”, meaning it’ll bottom out, and not a “through hole”. Don’t force the tap when it hits bottom. You can measure its depth by inserting something into it and marking how far it goes, but consider this only a guide and not definitive. The threads will not go totally to the hole’s bottom, so it the depth measures at .500", it may only be threaded .490", so don’t force things.