Like most important legal questions, the issue of the statute of limitations has already been pondered by the great legal minds of Seinfeld. (Season 3, Episode 17, "The Café")
PIP stands for 'Personal Injury Protection'. It's a mandatory feature of auto liability insurance policies written in Massachusetts. If you've been injured in a motor vehicle accident, you are entitled to coverage for your own medical expenses, lost wages and other expenses, no matter who was at fault. Your passengers are also covered by PIP benefits if they've been hurt.