Tapping sound from 4.3L engine in cold weather

There is a slight tapping sound coming from my 4.3L engine in cold weather at start-up. It goes away after a mile or so. No sound in warm weather. Might it be a valve problem? (111K miles.) Is it bad to leave as is?

I'm no expert, but this used to happen to my 69 Chevy Truck, it's a stuck lifter. When it's cold, the oil is thick, so the lifter won't move easily, but once the oil gets warm, the lifter moves easily. Might want to replace your lifters, it's not too tough of a job.