Wa `alaykum As-Salamu waRahmatullahi 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:
2- It is permissible to use botox if it is free from harm.
Answering your question, the Fatwa Center at Islam Q & A, states:
There is nothing wrong with breast implants or enlargement for one who has had a breast removed or who is suffering because they are small, because that comes under the heading of removing a fault or restoring something to the way it was created by Allah.
The evidence for that is the report narrated by Abu Dawud, At-Tirmidhi and An-Nas’I from `Abd al-Rahmaan ibn Tarafah, that the nose of his grandfather ‘Arjafah ibn As‘ad was cut off in the battle of Al-Kulaab, and he wore a nose made of silver, but it began to stink, so the Prophet (peace be upon him) told him to get a nose made of gold.
It is permissible to use botox if it is free from harm, because the Prophet (peace be upon him) said: “There should be neither harm nor reciprocating harm.” (Ahmad and Ibn Majah)
Almighty Allah knows best.