BPs. 2:7 explained by Heb. 5:1-5.
First, however, a quick recap of A above:
Ps. 2:1-2 is speaking of Jehovah and his Christ ("anointed"), and Acts 4:24-27 shows that Ps. 2:2 is speaking of the Father (Jehovah) and his Christ ("anointed") who is Jesus! So the two individuals in Psalm 2:1-2 are Jehovah (who cannot be the Son because of the following) and Jesus!
B.Hebrews 5:1-5 shows that Ps. 2:7 concerns God speaking to Jesus, His Son. But Ps. 2:7-8 shows Jehovah talking to Jesus and calling him Son. Hebrews 5:4 - And no man taketh this honour [high priest] unto himself, but he that is called of God, as [was] Aaron. 5 So also Christ glorified not himself to be made an high priest; but he [the Father] that said unto him, Thou art my Son, to day have I begotten thee. - KJV.
Psalm 2:7- I will declare the decree: the LORD [Jehovah] hath said unto me, Thou [art] my Son; this day have I begotten thee. 8 Ask of me, and I shall give [thee] the heathen [for] thine inheritance, and the uttermost parts of the earth [for] thy possession.
Clearly, Jehovah [mistranslated 'LORD,' all capitals] is the Father here!