Knock or click noise inside steering wheel??

I bought a used car in February. I've noticed in the last two weeks, about once per week, a knocking sound inside the steering wheel. Almost like a bolt sound clicking. It must've been after a turn, as I don't recall it just being straight and doing that. I checked power steering fluid and it's ok. Its only been twice in two weeks, so is it something to be concerned about like in the very near future, or just gauge it if it continues?