can we use the word sayyidina in durood for Prophet Muhhamed (P.B.U.h)

All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

If you mean mentioning the word ‘Sayyidina’ (which means our master) when reciting the Ibraaheemi salutations [that is recited in Tashahhud in prayer], then this should not be done, because it is better to say the wording that is mentioned in the Sunnah exactly as it is mentioned without the addition of this word (Sayyidina). However, if you mean saying it at other places than this, then this is permissible, like saying ‘salla Allaahu ‘ala Sayyidina Muhammad’. There is no doubt that he is our master. Allaah The Almighty has ordered us to honor him and respect him. Allaah Says (what means): {That you [people] may believe in Allaah and His Messenger and honor him and respect him [i.e. the Prophet ()] and exalt Him [i.e. Allaah] morning and afternoon.}[Quran 48:9]

At-Tabari said (while interpreting the above verse): “Allaah ordered us to honor him and respect him.”

For more benefit, please refer to Fatwa 88858.

Allaah Knows best.