I would contact Apple. Could be a fan issue or it could be the little part you suggest. But if you're not comfortable doing it on your own, definitely send it in. A friend of mine had his checked by Apple for what he said was the same thing, some ticking noise. Apple found out the fan was defective and replaced it. Maybe you could ship it to them. A hassle, sure, but the best way to know your MBP is good to go.