1999 Jeep Cherokee Car

Ticking isn't serious if it's up high in the engine. The hydraulic lifters are the last thing down the line to get pressurized oil and the first thing to make noise when that pressure is low. Once the oil is full enough so the pump doesn't draw up air, the ticking will slowly go away. Lifters that fill with air instead of oil do not stretch out to take up the play in the valve train. That makes the parts clatter and sound like a busy typewriter. Relatively little damage will occur from that, but if you continue to ignore the low oil and the clattering, other parts will fail next, and those are real serious.