Hi, I sold stocks with a small gain while living in MA and then moved to PA. How to fill out the section"Any double taxed income from Massachusetts?".Thanks

Since you were a part year resident of each state, there is no reason that PA would tax your MA income.

Part-Year Residents of Pennsylvania. Part-year residents are subject to PA personal income tax on all income earned, received and realized from all sources when residents of PA. Part-year residents are also subject to PA tax on income earned, received and realized from sources within PA when they were not a PA residents. Part-year residents are not subject to PA tax on ordinary interest, dividends, gains, intangible property or gambling and lottery winnings from PA sources while a nonresident.  Some exceptions apply; see below for additional detail.

Apportioning Income (Loss) on  PA Schedule NRH
As a nonresident, you may apportion income earned within and outside PA. Apportion PA-taxable compensation when your employer does not separately report PA wages on Form W-2. You must apportion income (loss) from operating a business within and outside Pennsylvania unless you maintain books and records that clearly substantiate and separately allocate your PA-source receipts, expenses, liabilities, etc.

PA PY