Is It Ok to Sleep on the Side with the Cheek Pressed Against Pillow/arm After Restylane Injection?

It's okay to sleep on your cheek after fillers, there is always asymmetry in the face. I suggest you give it a full 2-3 weeks for the swelling to settle before seeing your final result.

I suppose it is possible, but not very likely unless you were constantly pressing on it in your sleep. Remember there is always asymmetry in the face. One cheek is always larger due to underlying bony and soft tissue differences.

Unless you are sleeping on a board or with a flat weight on your face it is very doubtful that the unevenness in your Restylane is from your sleeping angle. Almost everyone has asymmetry to begin with so often people will have asymmetric swelling because as injectors we try to compensate for that. After 10-14 days your swelling overall should resolve and you can see how everything looks. "This answer has been solicited without seeing this patient and cannot
be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."