Did Hashem already hear?
Radak: No. Past tense is used in place of future in most Nevu'os. The same applies to "Nasata".
What Nedarim are discussed?
Radak #1: When David was exiled, he vowed, if Hashem will return him to Eretz Yisrael safely
What is the meaning of "Nasata Yerushas Yir'ei Shemecha"?
Rashi: You returned the cities of [Yisrael's] inheritance via me.
Radak #2: This is the Ohel Mo'ed (if the verse discusses David) or the Beis ha'Mikdash (if it discusses Galus). It is the inheritance of Yir'ei Hashem. Give to me this gift, that I will dwell in the inheritance of those who fear Your name.
Malbim: You promised kingship to me and my seed, when they are Yir'ei Shemecha - "Im Yishmeru Vanecha Brisi
