Hyaluronic acid is not an exfoliating acid
Despite the name, hyaluronic acid is a humectant, not an AHA or BHA. It is used to help formulas hold water near the skin surface and does not create the same exfoliation concerns as glycolic or salicylic acid.
Where it fits on a retinol night
A hyaluronic-acid serum can sit under moisturizer, or you can skip the separate serum and use a moisturizer that already contains humectants. Retinol remains the treatment step. Follow the directions for the specific retinol rather than forcing every product into a universal layering order.
Be thoughtful about damp skin
People often apply humectants to slightly damp skin. That can be comfortable, but some retinoid users prefer their skin fully dry before applying the retinoid because damp skin may make certain formulas spread or penetrate differently and feel more irritating. If your retinol instructions specify dry skin, follow them.
You may not need another bottle
A basic moisturizer already combines humectants, emollients and occlusive ingredients. If your skin feels comfortable, a separate hyaluronic-acid serum is optional. More hydration steps are not automatically better, especially if they make the routine pill or tempt you to rub the skin repeatedly.
If the routine still feels dry
Do not keep adding watery serums while ignoring the moisturizer. Reduce retinol frequency if irritation is accumulating, choose a richer moisturizer if appropriate, and protect the skin from additional exfoliation until it settles.