Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Responding to your question, Dr. Wael Shihab, PhD in Islamic Studies from Al-Azhar University, and currently the Imam of the Downtown Toronto Masjid in Canada, states,
Sujud, according to the majority of Muslim scholars, counts when one puts his or her forehead on the ground/floor. This is the view of the Hanafi and Maliki scholars. It is approved of by the Shafi`i and Hanbali scholars according to some reports. Prostrating by other organs of sujud—such as the hands—is recommended and not obligatory.
Given the above, raising some or all fingertips will not invalidate your prayer.
Allah Almighty knows best.