I burned my lip on a fry from McDonald's, should I pursue a monetary payoff?

Not likely to be successful or good use of your time.

You can try but unless there is a history of fries being served at an excessively hot temperature (ala the coffee case) you may not have cause of action. Confirm with local counsel.

Did you get medical treatment? I don't see a lawyer taking this case. If you picked up the fry with you finger, you should have known it was hot. You can report to McD's and maybe they'll give you a voucher for free food.

First - You do not get a windfall from minor, everyday occurrences. The world is a dangerous place and a lip burn on a fry is really not that unexpected. Second - liability would be difficult to prove unless you could show that -- somehow - the temperature of the fry was extreme. Moreover, a week has passed. if you did not make a report, how would you prove the blister was a McDonald's related fry. Third - what are your damages? A blister really is not something that is compensable in any real way. If it was compensable, chocolate manufacturers may be sued for giving people zits. You can pursue it, but IU don't think you will find there is much to pursue.

Fortunately lips heal quickly. Maybe McDonalds will give you some coupons

No. Best bet is to stop eating this garbage, and start eating some healthy organic food.